Humidification-dehumidification systems and methods at low top brine temperatures

ABSTRACT

Embodiments described generally relate to systems comprising a humidifier (e.g., a bubble column humidifier) and a heating device (e.g. a heat exchanger), and associated methods. In certain embodiments, the heating device heats a first liquid stream comprising a condensable fluid in liquid phase (e.g., water) and a dissolved salt (e.g., NaCl) to a relatively low temperature (e.g., about 90° C. or less) prior to the first liquid stream entering the humidifier through a main humidifier liquid inlet. In some cases, the system comprising the humidifier and the heating device requires only low-grade heat to operate, which may be advantageous due to the low cost and high availability of such heat.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.15/161,051, filed May 20, 2016, and entitled“Humidification-Dehumidification Systems and Methods at Low Top BrineTemperatures,” which is incorporated herein by reference in its entiretyfor all purposes.

TECHNICAL FIELD

Disclosed embodiments generally relate to systems comprising ahumidifier and a heating device, and associated methods.

BACKGROUND

Fresh water shortages are becoming an increasing problem around theworld, with demand for fresh water for human consumption, irrigation,and/or industrial use continuing to grow. In order to meet the growingdemand for fresh water, various desalination methods may be used toproduce fresh water from salt-containing water such as seawater,brackish water, water produced from oil and/or gas extraction processes,flowback water, and/or wastewater. For example, one desalination methodis a humidification-dehumidification (HDH) process, which involvescontacting salt-containing water with a carrier gas in a humidifier,such that the carrier gas becomes heated and humidified. The heated andhumidified gas is then brought into contact with cold water in adehumidifier, thereby producing purified water.

However, HDH systems and processes often involve certain drawbacks. Forexample, an influent stream is often heated to a relatively hightemperature prior to being introduced into a humidifier of an HDH systemin order to increase efficiency and/or production rate of the system. Insome cases, the heating step may require relatively large amounts ofenergy, which may be expensive and/or difficult to obtain. HDH systemswith improved properties, such as lower temperature requirements forinfluent streams, are therefore desirable.

SUMMARY

Systems comprising a humidifier and a heating device, and associatedmethods, are disclosed. The subject matter of the present inventioninvolves, in some cases, interrelated products, alternative solutions toa particular problem, and/or a plurality of different uses of one ormore systems and/or articles.

Some aspects relate to a system comprising a humidifier. According tosome embodiments, the humidifier comprises a main humidifier liquidinlet; a main humidifier gas inlet; a main humidifier liquid outlet; anintermediate humidifier liquid outlet; a main humidifier gas outlet; anda plurality of stages. In certain embodiments, the plurality of stagescomprises a first stage, a last stage, and one or more intermediatestages positioned between the first stage and the last stage. In certainembodiments, the intermediate humidifier liquid outlet is a liquidoutlet of the first stage or one of the one or more intermediate stages.According to some embodiments, the system further comprises a firstheating device. In certain embodiments, a first liquid inlet of thefirst heating device comprises or is fluidically connected to theintermediate humidifier liquid outlet. In certain embodiments, a firstliquid outlet of the first heating device comprises or is fluidicallyconnected to the main humidifier liquid inlet. In some embodiments, thefirst liquid inlet of the first heating device is configured to receivea first liquid stream comprising a condensable fluid in liquid phase anda dissolved salt. In some embodiments, the main humidifier gas inlet isconfigured to receive a gas stream comprising a non-condensable gas.

Some aspects relate to a method of operating a humidifier. According tosome embodiments, the method comprises flowing a first liquid streamcomprising a condensable fluid in liquid phase and a dissolved saltthrough a first fluidic pathway of a first heating device. In certainembodiments, the first liquid stream is heated within the first heatingdevice to form a heated first liquid stream. In some embodiments, themethod further comprises injecting the heated first liquid stream into amain liquid inlet of a humidifier comprising a plurality of stages. Incertain embodiments, the plurality of stages comprises a first stage, alast stage, and one or more intermediate stages positioned between thefirst stage and the last stage. In some embodiments, the method furthercomprises injecting a gas stream comprising a non-condensable gas into amain gas inlet of the humidifier. In some embodiments, the methodfurther comprises flowing the heated first liquid stream through thehumidifier in a first direction from the first stage to the last stageand simultaneously flowing the gas stream through the humidifier in asecond direction from the last stage to the first stage. In certainembodiments, heat and mass are transferred from the heated first liquidstream to the gas stream to produce a vapor-containing humidifier gasoutlet stream and a concentrated liquid stream. In some embodiments, themethod further comprises flowing an extracted liquid stream comprisingat least a portion of the concentrated liquid stream from anintermediate liquid outlet of the humidifier to the first heatingdevice. In certain embodiments, the intermediate liquid outlet of thehumidifier is a liquid outlet of the first stage or one of the one ormore intermediate stages of the humidifier.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying figures. In cases where the present specification and adocument incorporated by reference include conflicting and/orinconsistent disclosure, the present specification shall control. If twoor more documents incorporated by reference include conflicting and/orinconsistent disclosure with respect to each other, then the documenthaving the later effective date shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale. In the figures,each identical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled in every figure, nor is every component of eachembodiment of the invention shown where illustration is not necessary toallow those of ordinary skill in the art to understand the invention. Inthe figures:

FIG. 1 shows, according to some embodiments, a schematic diagram of anexemplary system comprising a multi-stage humidifier and a heatingdevice;

FIG. 2 shows a schematic diagram of an exemplary system comprising amulti-stage humidifier, a multi-stage dehumidifier, and a heatingdevice, according to some embodiments;

FIG. 3A shows, according to some embodiments, a schematic diagram of anexemplary system comprising a multi-stage humidifier, a multi-stagedehumidifier, a heating device, a heat exchanger, a first tank, and asecond tank, where a first liquid outlet of the heat exchanger isfluidically connected to a first liquid inlet of the heating device; and

FIG. 3B shows, according to some embodiments, a schematic diagram of anexemplary system comprising a multi-stage humidifier, a multi-stagedehumidifier, a heating device, a heat exchanger, a first tank, and asecond tank, where a first liquid outlet of the heat exchanger isfluidically connected to an intermediate liquid inlet of the humidifier;

FIG. 4 shows a schematic diagram of an exemplary system comprising amulti-stage humidifier, a multi-stage dehumidifier, a heating device, aheat exchanger, a storage tank, and an air-cooled heat exchanger,according to some embodiments;

FIG. 5A shows, according to some embodiments, a plot of production rate,gained output ratio (GOR), and top liquid temperature as a function ofthe percent of water extracted after the top tray for experimentsconducted on a system thermally balanced for an initial top liquidtemperature of 180° F.; and

FIG. 5B shows, according to some embodiments, a plot of production rate,gained output ratio (GOR), and top liquid temperature as a function ofthe percent of water extracted after the top tray for experimentsconducted on a system thermally balanced for an initial top liquidtemperature of 192° F.

DETAILED DESCRIPTION

Embodiments described herein generally relate to systems comprising ahumidifier (e.g., a bubble column humidifier) and a heating device, andassociated methods. In certain embodiments, the heating device heats afirst liquid stream comprising a condensable fluid in liquid phase(e.g., water) and a dissolved salt (e.g., NaCl) to a relatively lowtemperature (e.g., about 90° C. or less) prior to the first liquidstream entering the humidifier through a main humidifier liquid inlet.In some cases, the system comprising the humidifier and the heatingdevice requires only low-grade heat to operate, which may beadvantageous due to the low cost and high availability of such heat.

In some embodiments, the first liquid stream flows through thehumidifier in a first direction, and a gas stream comprising anon-condensable gas (e.g., air) flows through the humidifier in a seconddirection. Within the humidifier, heat and mass may be transferred fromthe first liquid stream to the gas stream (e.g., via evaporation) toproduce a vapor-containing humidifier gas outlet stream enriched in thecondensable fluid in vapor phase relative to the gas stream and aconcentrated liquid stream enriched in the dissolved salt relative tothe first liquid stream. In some embodiments, a portion of theconcentrated liquid stream exits the humidifier through an intermediatehumidifier liquid outlet and is recirculated through a fluidic circuitcomprising the intermediate humidifier liquid outlet, a first liquidinlet of the heating device, a first liquid outlet of the heatingdevice, and the main humidifier liquid inlet. The remaining portion ofthe concentrated liquid stream may continue to flow through thehumidifier, thereby becoming further concentrated, and may exit thehumidifier through a main humidifier liquid outlet. In some embodiments,the humidifier may be fluidically connected to a dehumidifier (e.g., abubble column condenser). The humidifier and dehumidifier may be used inwater purification systems, such as desalination systems.

Previous humidification-dehumidification (HDH) systems were oftenoperated with relatively high influent temperatures. That is to say, insuch previous HDH systems, an influent liquid stream was often heated toa relatively high temperature (e.g., greater than about 90° C.) prior tobeing introduced into a humidifier of an HDH system in order to increasethe efficiency and/or production rate of the HDH system. However, newhumidifier and HDH systems and methods have been developed within thecontext of this invention that can, in certain cases, have relativelyhigh operating efficiency and/or may be able to be operated effectivelyusing relatively low liquid influent temperatures (e.g., less than about90° C.).

Certain aspects relate to a humidifier system comprising a fluidiccircuit comprising an intermediate liquid outlet of a humidifier, afirst liquid inlet of a heating device, a first liquid outlet of theheating device, and a main liquid inlet of the humidifier. In somecases, recirculation of a liquid stream through the fluidic circuit mayincrease the liquid mass flow rate through a first stage of thehumidifier and may compensate for the relatively low temperature of theinfluent liquid stream (e.g., a first liquid stream comprising acondensable fluid in liquid phase and a dissolved salt). For example,the operation of certain embodiments may be characterized by Equation 1:

{dot over (m)}_(liquid,i)ΔT_(liquid,i)C={dot over(m)}_(liquid,f)ΔT_(liquid,f)C=Δ{dot over (H)}_(gas)=constant   (1)

where {dot over (m)}_(liquid, i) represents a first mass flow rate ofthe influent liquid stream (e.g., a first mass flow rate of the firstliquid stream at the main humidifier liquid inlet), ΔT_(liquid,i)represents a first temperature change of the influent liquid streamacross the first stage of the humidifier (e.g., the difference betweenthe temperature of the first liquid stream at the main humidifier liquidinlet and the temperature of the first liquid stream at a liquid outletof the first stage of the humidifier), C represents the heat capacity ofthe influent liquid stream, {dot over (m)}_(liquid,f) represents asecond mass flow rate of the influent liquid stream (e.g., a second massflow rate of the first liquid stream at the main humidifier liquidinlet), ΔT_(liquid,f) represents a second temperature change of theinfluent liquid stream across the first stage of the humidifier, andΔ{dot over (H)}_(gas) represents the enthalpy rate change of a gasstream in thermal contact with the influent liquid stream. Equation 1demonstrates that, for a liquid stream and a gas stream in thermalcontact, an increase in liquid mass flow rate may compensate for adecrease in liquid temperature change such that the enthalpy rate changeof the gas stream remains constant. For example, if the secondtemperature change of the influent liquid stream across the firsthumidifier stage is less than the first temperature change of theinfluent liquid stream across the first humidifier stage, the enthalpyrate change of the gas stream in thermal contact with the influentliquid stream may remain constant if the second mass flow rate of theinfluent liquid stream is greater than the first mass flow rate of theinfluent liquid stream. Accordingly, even if the influent liquid streamhas a relatively low temperature, an increased liquid mass flow rate inthe first stage of the humidifier may allow the enthalpy rate change ofthe gas stream to remain relatively constant. In some cases, temperaturemay be represented as a function of enthalpy, and a relatively constantchange in enthalpy rate of the gas stream may indicate that thetemperature change of the gas stream is also relatively constant. Thatis to say, the increased liquid mass flow rate may allow a sufficientamount of heat to be transferred from the influent liquid stream to thegas stream, such that the temperature of the gas stream is increased toa target temperature identified as resulting in optimal efficiencyand/or production.

In some embodiments, removal of at least a portion of the liquid streamwithin the humidifier through an intermediate humidifier liquid outletmay isolate/mitigate the effect of the increased liquid mass flow rate,such that optimal thermal balancing is maintained in the humidifierwithout the need to substantially increase the size/capacity of theentire humidifier.

A system (e.g., an HDH system) with a relatively low influenttemperature may be further advantageous, in some cases, because it mayallow for operation of the system using low-grade heat (e.g., heathaving a temperature of about 90° C. or less). In some cases, low-gradeheat may be abundantly available at a relatively low cost (or, incertain cases, no cost). For example, low-grade heat may be availablefrom natural heat sources, such as geothermal heat sources and solarradiation. In addition, many industrial processes (e.g., oil refining,metal refining) produce low-grade waste heat, and many cogenerationplants produce hot water or steam in addition to electricity. Even ifconventional heating sources (e.g., furnaces) are used, it may becheaper to obtain low-grade heat than high-temperature heat because, forexample, due to reduced fuel costs associated with operating suchheaters and/or the ability to operate conventional heating sources belowthe boiling point of a liquid being heated (e.g., a heating fluid),resulting in lower pressure requirements and lower associated capitaland operating costs. In certain embodiments described, such low-gradeheat sources may be used to heat an influent liquid stream prior to thestream entering the humidifier.

While embodiments of the invention may employ a variety of humidifierdesigns, including but not limited to those involving direct contactbetween gas and liquid streams, certain types of humidifiers may beassociated with advantages over other types of humidifiers. For example,bubble column humidifiers may exhibit higher thermodynamic efficiencythan certain other types of humidifiers (e.g., certain packed bedhumidifiers, spray towers, wetted wall towers). Without wishing to bebound by a particular theory, the increased thermodynamic efficiency ofbubble column humidifiers may be at least partially attributed to theuse of gas bubbles for heat and mass transfer, since gas bubbles mayhave more surface area available for heat and mass transfer than manyother types of surfaces (e.g., typical packing material). As describedin further detail below, a bubble column humidifier may have certainfeatures that further increase thermodynamic efficiency, including, butnot limited to, relatively low liquid level height, relatively highaspect ratio liquid flow paths, and multi-staged designs. In certaincases, bubble column humidifiers may be particularly well-suited forcertain of the presently described systems due to the relatively highrates of heat and mass transfer that may be attainable with certain ofthose humidifiers.

FIG. 1 is a schematic diagram of an exemplary system 100 comprisinghumidifier 102 and heating device 104. As shown in FIG. 1, humidifier102 comprises a plurality of stages 102A-102E, including first stage102A, last stage 102E, and intermediate stages 102B-102D. A first liquidinlet 122 of heating device 104 comprises or is fluidically connected toan intermediate liquid outlet 128 of humidifier 102 and a main liquidoutlet 130 of humidifier 102.

In addition, a first liquid outlet 124 of heating device 104 comprisesor is fluidically connected to a main liquid inlet 126 of humidifier102. In some cases, heating device 104 may also be fluidically connectedto a source of a liquid stream comprising a condensable fluid in liquidphase and a dissolved salt (not shown in FIG. 1).

In operation, heating device 104 may receive a first liquid stream 106comprising a condensable fluid in liquid phase and a dissolved saltthrough first liquid inlet 122. Within heating device 104, first liquidstream 106 may be heated to produce heated first liquid stream 108.Heated first liquid stream 108 may then be directed to flow from firstliquid outlet 124 of heating device 104 to main liquid inlet 126 ofhumidifier 102. In some cases, the temperature of heated first liquidstream 108 at main liquid inlet 126 of humidifier 102 is relatively low(e.g., about 90° C. or less). Upon entering first humidifier stage 102A,which comprises or is fluidically connected (e.g., directly fluidicallyconnected) to main liquid inlet 126 of humidifier 102, heated firstliquid stream 108 may come into contact within humidifier 102 with gasstream 112, which may comprise a non-condensable gas. Gas stream 112 mayenter humidifier 102 through main humidifier gas inlet 132 that isfluidically connected (e.g., directly fluidically connected) to lasthumidifier stage 102E and may flow through humidifier 102 from lasthumidifier stage 102E to first humidifier stage 102A.

In first humidifier stage 102A, heat and mass may be transferred fromheated first liquid stream 108 to gas stream 112 (e.g., via anevaporation process), thereby producing a cooled, concentrated liquidstream enriched in the dissolved salt relative to heated first liquidstream 108 and a heated, at least partially humidified gas streamenriched in the condensable fluid in vapor phase relative to gas stream112 received in the main humidifier gas inlet. The heated, at leastpartially humidified gas stream may exit humidifier 102 through a mainhumidifier gas outlet as vapor-containing humidifier gas outlet stream114. An extracted liquid stream 110 comprising at least a portion of thecooled, concentrated liquid stream may exit humidifier 102 throughintermediate humidifier liquid outlet 128 and may be directed to flow tofirst liquid inlet 122 of heating device 104. The remaining portion ofthe cooled, concentrated liquid stream may continue to flow throughhumidifier 102 from first humidifier stage 102A to last humidifier stage102E, thereby becoming further cooled and concentrated (i.e., enrichedin the dissolved salt). The cooled, concentrated liquid stream may exithumidifier 102 as humidifier liquid outlet stream 116 through mainhumidifier liquid outlet 130 in fluidic communication with (e.g.,directly fluidically connected to) last humidifier stage 102E.

In certain embodiments, at least a portion 118 of humidifier liquidoutlet stream 116 is discharged from system 100. In certain cases, thedischarge rate of at least a portion of humidifier liquid outlet stream116 may be selected to maintain a steady-state system salinity. In someembodiments, all of humidifier liquid outlet stream 116 is dischargedfrom system 100. In some embodiments, at least a portion 120 ofhumidifier liquid outlet stream 116 remains within system 100 and iscombined with extracted liquid stream 110 and additional influent liquid(e.g., first liquid stream 106) before being returned to heating device104 and recirculated to humidifier 102.

According to some embodiments, a heating device may heat an influentliquid stream (e.g., a first liquid stream comprising a condensablefluid in liquid phase and a dissolved salt) to a relatively lowtemperature (e.g., about 90° C. or less), and the heated influent liquidstream may enter a humidifier at a relatively low temperature. In someembodiments, the temperature of an influent liquid stream entering thehumidifier at a main humidifier liquid inlet (e.g., a liquid inletdirectly fluidically connected to a first humidifier stage) is about 90°C. or less, about 80° C. or less, about 70° C. or less, about 60° C. orless, about 50° C. or less, about 40° C. or less, or about 30° C. orless. In certain embodiments, the temperature of an influent liquidstream entering the humidifier at a main humidifier liquid inlet is inthe range of about 30° C. to about 50° C., about 30° C. to about 60° C.,about 30° C. to about 70° C., about 30° C. to about 80° C., about 30° C.to about 90° C., about 40° C. to about 60° C., about 40° C. to about 70°C., about 40° C. to about 80° C., about 40° C. to about 90° C., about50° C. to about 70° C., about 50° C. to about 80° C., about 50° C. toabout 90° C., about 60° C. to about 80° C., about 60° C. to about 90°C., or about 70° C. to about 90° C. The temperature of the influentliquid stream may be measured at the main humidifier liquid inletaccording to any method known in the art. For example, the temperaturemay be measured using one or more thermocouples (e.g., Type Kthermocouples). In some embodiments, an extracted liquid stream (e.g., astream comprising at least a portion of a cooled, concentrated liquidstream) exits the humidifier through an intermediate humidifier liquidoutlet. As used herein, an intermediate humidifier liquid outlet refersto a liquid outlet of a first stage or an intermediate stage of ahumidifier comprising at least three stages. In certain embodiments, thelocation of extraction is selected such that the temperature of theextracted liquid stream differs with respect to the temperature of aninfluent liquid stream entering a heating device (e.g., a first liquidstream comprising a condensable fluid in liquid phase and a dissolvedsalt, a pre-heated first liquid stream) by only a relatively smallamount. In some embodiments, the temperature difference is about 10° C.or less, about 5° C. or less, about 2° C. or less, or about 1° C. orless. In certain embodiments, the temperature difference is in the rangeof about 0° C. to about 10° C., about 0° C. to about 5° C., about 0° C.to about 2° C., or about 0° C. to about 1° C.

The extracted liquid stream may exit the humidifier at a certain flowrate selected to optimize the thermal efficiency of the humidifier. Forexample, in certain embodiments in which the temperature of the liquidstream entering the humidifier is relatively low, the flow rate of theextracted liquid stream may be adjusted (e.g., increased or decreased)to maintain an optimal temperature of the gas stream and the liquidstream exiting the first humidifier stage.

In some cases, the optimal temperature of the gas stream and/or liquidstream flowing through the humidifier refers to the temperature(s) atwhich the heat capacity rate ratio (HCR) of the humidifier approachesone. In some embodiments, the HCR of the humidifier may be calculatedaccording to Equation 2:

$\begin{matrix}{{H\; C\; R} = \left( \frac{\Delta {\overset{.}{H}}_{\max,c}}{\Delta {\overset{.}{H}}_{\max,h}} \right)} & (2)\end{matrix}$

where the numerator, Δ{dot over (H)}_(max,c), is the maximum enthalpyrate change of a cold stream flowing through the humidifier (e.g., thegas stream) and the denominator, Δ{dot over (H)}_(max,h), is the maximumenthalpy rate change of a hot stream flowing through the humidifier(e.g., the liquid stream). In the case of a dehumidifier, the coldstream would refer to a liquid stream flowing through the dehumidifier,and the hot stream would refer to a gas stream flowing through thedehumidifier.

The maximum enthalpy rate change of a stream refers to the enthalpy ratechange that would occur if the stream reached, at the main humidifieroutlet, the inlet temperature of the other stream. For example, themaximum enthalpy rate change of the hot stream (e.g., the liquid streamin the humidifier) can be approximated according to Equation 1 as theproduct of the mass flow rate of the influent liquid stream at the mainhumidifier liquid inlet, the heat capacity of the liquid, and thedifference between the temperature of the influent liquid stream at themain humidifier liquid inlet and the temperature of the influent gasstream at the main humidifier gas inlet. The maximum enthalpy ratechange of the cold stream (e.g., the gas stream in the humidifier) canbe approximated as the difference between the enthalpy rate of the gasstream at the main humidifier gas inlet (the product of the mass flowrate of the influent gas stream at the main humidifier gas inlet, thespecific heat capacity of the gas at the temperature and humidity ratioof the influent gas stream at the main humidifier gas inlet, and thetemperature of the influent gas stream at the main humidifier gas inlet)and the enthalpy rate of the gas stream at the main humidifier gasoutlet (the product of the mass flow rate of the influent gas stream atthe main humidifier gas inlet, the specific heat capacity of the gas atthe temperature of the influent liquid stream at the main humidifierliquid inlet and the saturated humidity ratio at that temperature, andthe temperature of the influent liquid stream at the main humidifierliquid inlet). In certain cases, the temperature(s) and/or flow rate(s)of the liquid and/or gas streams flowing through the humidifier areselected such that the HCR is between about 0.5 and about 1.5, betweenabout 0.6 and about 1.4, between about 0.7 and about 1.3, between 0.8and about 1.2, between about 0.9 and about 1.1, or between about 0.95and about 1.05.

According to some embodiments, the extracted liquid stream exits thehumidifier through an intermediate humidifier liquid outlet at a lowerflow rate than the humidifier liquid outlet stream exits the humidifierthrough the main humidifier liquid outlet. In certain embodiments, theflow rate of the extracted liquid stream at the intermediate humidifierliquid outlet is at least about 5%, at least about 10%, at least about20%, at least about 25%, at least about 30%, at least about 40%, or atleast about 50% of the flow rate of the humidifier liquid outlet streamat the main humidifier liquid outlet. In some embodiments, the flow rateof the extracted liquid stream at the intermediate humidifier liquidoutlet is about 50% or less, about 40% or less, about 30% or less, about25% or less, about 20% or less, about 10% or less, or about 5% or lessof the flow rate of the humidifier liquid outlet stream at the mainhumidifier liquid outlet. In some embodiments, the flow rate of theextracted liquid stream at the intermediate humidifier liquid outlet isbetween about 5% and about 10%, about 5% and about 20%, about 5% andabout 25%, about 5% and about 30%, about 5% and about 40%, about 5% andabout 50%, about 10% and about 20%, about 10% and about 25%, about 10%and about 30%, about 10% and about 40%, about 10% and about 50%, about20% and about 30%, about 20% and about 40%, about 20% and about 50%,about 25% and about 40%, about 25% and about 50%, about 30% and about40%, about 30% and about 50%, or about 40% and about 50% of the flowrate of the humidifier liquid outlet stream at the main humidifierliquid outlet. The flow rate of the extracted liquid stream at theintermediate humidifier liquid outlet and the flow rate of thehumidifier liquid outlet stream at the main humidifier liquid outlet maybe measured according to any suitable method known in the art. Forexample, the flow rates may be measured using one or more flow meters(e.g., paddle wheel flow meters, rotameters, ultrasonic flow meters,mass flow meters).

According to some embodiments, the extracted liquid stream exits thehumidifier through the intermediate humidifier liquid outlet at a higherflow rate than the humidifier liquid outlet stream exits the humidifierthrough the main humidifier liquid outlet. In certain embodiments, theflow rate of the extracted liquid stream at the intermediate humidifierliquid outlet is at least about 105%, at least about 110%, at leastabout 120%, at least about 125%, at least about 130%, at least about140%, or at least about 150% of the flow rate of the humidifier liquidoutlet stream at the main humidifier liquid outlet. In some embodimentsthe flow rate of the extracted liquid stream at the intermediatehumidifier liquid outlet is about 150% or less, about 140% or less,about 130% or less, about 125% or less, about 120% or less, about 110%or less, or about 105% or less of the flow rate of the humidifier liquidoutlet stream at the main humidifier liquid outlet. In some embodiments,the flow rate of the extracted liquid stream at the intermediatehumidifier liquid outlet is between about 105% and about 110%, about105% and about 120%, about 105% and about 125%, about 105% and about130%, about 105% and about 140%, about 105% and about 150%, about 110%and about 120%, about 110% and about 125%, about 110% and about 130%,about 110% and about 140%, about 110% and about 150%, about 120% andabout 130%, about 120% and about 140%, about 120% and about 150%, about125% and about 140%, about 125% and about 150%, about 130% and about140%, about 130% and about 150%, or about 140% and about 150% of theflow rate of the humidifier liquid outlet stream at the main humidifierliquid outlet.

In certain embodiments comprising a desalination system that has theexemplary configuration illustrated in FIG. 3A and that is configured toproduce about 800 barrels of substantially pure water per day, theextracted liquid stream has a flow rate at the intermediate humidifierliquid outlet of at least about 30 gpm, at least about 40 gpm, at leastabout 50 gpm, at least about 100 gpm, at least about 150 gpm, at leastabout 200 gpm, at least about 250 gpm, at least about 300 gpm, at leastabout 350 gpm, at least about 400 gpm, at least about 450 gpm, at leastabout 500 gpm, at least about 550 gpm, or at least about 600 gpm. Incertain embodiments, the extracted liquid stream has a flow rate at theintermediate humidifier liquid outlet in the range of about 30 gpm toabout 50 gpm, about 30 gpm to about 100 gpm, about 30 gpm to about 150gpm, about 30 gpm to about 200 gpm, about 30 gpm to about 300 gpm, about30 gpm to about 400 gpm, about 30 gpm to about 500 gpm, about 30 gpm toabout 600 gpm, about 50 gpm to about 100 gpm, about 50 gpm to about 200gpm, about 50 gpm to about 300 gpm, about 50 gpm to about 400 gpm, about50 gpm to about 500 gpm, about 50 gpm to about 600 gpm, about 100 gpm toabout 200 gpm, about 100 gpm to about 300 gpm, about 100 gpm to about400 gpm, about 100 gpm to about 500 gpm, about 100 gpm to about 600 gpm,about 200 gpm to about 600 gpm, about 300 gpm to about 600 gpm, about400 gpm to about 600 gpm, or about 500 gpm to about 600 gpm.

In some embodiments, the extracted liquid stream may recirculate througha fluidic circuit comprising the intermediate humidifier liquid outlet,a first liquid inlet of a heating device, a first liquid outlet of theheating device, and a main humidifier liquid inlet. In certain cases,amounts of liquid may be added or removed from the fluidic circuit tocontrol the salinity of the recirculating liquid stream. For example,the amount of liquid recirculating through the fluidic circuit may beadjusted (e.g., increased or decreased) by increasing or decreasingextraction and/or injection flow rates at various points throughout thefluidic circuit. In some cases, liquid replacement in the fluidiccircuit may be substantially continuous, discontinuous (e.g., batch), orsemi-discontinuous (e.g., semi-batch).

In some embodiments, the heating device is configured to receive a firstliquid stream comprising a condensable fluid in liquid phase containinga dissolved salt. A condensable fluid generally refers to a fluid thatis able to convert from liquid phase to vapor phase under at least oneset of operating conditions within the humidifier. Non-limiting,illustrative examples of suitable condensable fluids include water,ammonia, benzene, toluene, ethyl benzene, alcohols, and/or combinationsthereof. In addition to the condensable fluid in liquid phase, the firstliquid stream may further comprise one or more additional liquids (e.g.,the liquid stream may be a liquid mixture). A dissolved salt generallyrefers to a salt that has been solubilized to such an extent that thecomponent ions (e.g., an anion, a cation) of the salt are no longerionically bonded to each other. Non-limiting examples of dissolved saltsthat may be present in the first liquid stream include sodium chloride(NaCl), sodium bromide (NaBr), potassium chloride (KCl), potassiumbromide (KBr), ammonium chloride (NH₄Cl), calcium chloride (CaCl₂),magnesium chloride (MgCl₂), sodium carbonate (Na₂CO₃), sodiumbicarbonate (NaHCO₃), potassium bicarbonate (KHCO₃), sodium sulfate(Na₂SO₄), potassium sulfate (K₂SO₄), calcium sulfate (CaSO₄), magnesiumsulfate (MgSO₄), strontium sulfate (SrSO₄), barium sulfate (BaSO₄),barium-strontium sulfate (BaSr(SO₄)₂), calcium nitrate (Ca(NO₃)₂), iron(III) hydroxide (Fe(OH)₃), iron (III) carbonate (Fe₂(CO₃)₃), aluminumhydroxide (Al(OH)₃), aluminum carbonate (Al₂(CO₃)₃), ammonium carbonate,ammonium bicarbonate, ammonium sulfate, boron salts, polyacrylic acidsodium salts, and/or silicates.

In certain embodiments, the first liquid stream comprisessalt-containing water (e.g., water comprising one or more dissolvedsalts). In certain cases, the salt-containing water comprises seawater,brackish water, water produced form an oil and/or gas extractionprocess, flowback water, and/or wastewater (e.g., industrialwastewater). Non-limiting examples of wastewater include textile millwastewater, leather tannery wastewater, paper mill wastewater, coolingtower blowdown water, flue gas desulfurization wastewater, landfillleachate water, and/or the effluent of a chemical process (e.g., theeffluent of another desalination system and/or chemical process).

In some embodiments, the first liquid stream has a relatively highconcentration of the dissolved salt. In certain embodiments, theconcentration of the dissolved salt in the first liquid stream is atleast about 1,000 mg/L, at least about 5,000 mg/L, at least about 10,000mg/L, at least about 50,000 mg/L, at least about 100,000 mg/L, at leastabout 150,000 mg/L, at least about 200,000 mg/L, at least about 250,000mg/L, at least about 300,000 mg/L, at least about 350,000 mg/L, or atleast about 375,000 mg/L (and/or, in certain embodiments, up to thesolubility limit of the dissolved salt in the liquid stream). In someembodiments, the concentration of the dissolved salt in the first liquidstream is in the range of about 1,000 mg/L to about 10,000 mg/L, about1,000 mg/L to about 50,000 mg/L, about 1,000 mg/L to about 100,000 mg/L,about 1,000 mg/L to about 150,000 mg/L, about 1,000 mg/L to about200,000 mg/L, about 1,000 mg/L to about 250,000 mg/L, about 1,000 mg/Lto about 300,000 mg/L, about 1,000 mg/L to about 350,000 mg/L, about1,000 mg/L to about 375,000 mg/L, about 10,000 mg/L to about 50,000mg/L, about 10,000 mg/L to about 100,000 mg/L, about 10,000 mg/L toabout 150,000 mg/L, about 10,000 mg/L to about 200,000 mg/L, about10,000 mg/L to about 250,000 mg/L, about 10,000 mg/L to about 300,000mg/L, about 10,000 mg/L to about 350,000 mg/L, about 10,000 mg/L toabout 375,000 mg/L, about 50,000 mg/L to about 100,000 mg/L, about50,000 mg/L to about 150,000 mg/L, about 50,000 mg/L to about 200,000mg/L, about 50,000 mg/L to about 250,000 mg/L, about 50,000 mg/L toabout 300,000 mg/L, about 50,000 mg/L to about 350,000 mg/L, about50,000 mg/L to about 375,000 mg/L, about 100,000 mg/L to about 150,000mg/L, about 100,000 mg/L to about 200,000 mg/L, about 100,000 mg/L toabout 250,000 mg/L, about 100,000 mg/L to about 300,000 mg/L, about100,000 mg/L to about 350,000 mg/L, about 100,000 mg/L to about 375,000mg/L, about 150,000 mg/L to about 200,000 mg/L, about 150,000 mg/L toabout 250,000 mg/L, about 150,000 mg/L to about 300,000 mg/L, about150,000 mg/L to about 350,000 mg/L, about 150,000 mg/L to about 375,000mg/L, about 200,000 mg/L to about 250,000 mg/L, about 200,000 mg/L toabout 300,000 mg/L, about 200,000 mg/L to about 350,000 mg/L, about200,000 mg/L to about 375,000 mg/L, about 250,000 mg/L to about 300,000mg/L, about 250,000 mg/L to about 350,000 mg/L, about 250,000 mg/L toabout 375,000 mg/L, about 300,000 mg/L to about 350,000 mg/L, or about300,000 mg/L to about 375,000 mg/L. The concentration of a dissolvedsalt generally refers to the combined concentrations of the cation andthe anion of the salt. For example, the concentration of dissolved NaClwould refer to the sum of the concentration of sodium ions (Nat) and theconcentration of chloride ions (Cl⁻). The concentration of the dissolvedsalt may be measured according to any suitable method known in the art.For example, methods for measuring the concentration of the dissolvedsalt include inductively coupled plasma (ICP) spectroscopy (e.g.,inductively coupled plasma optical emission spectroscopy). As onenon-limiting example, an Optima 8300 ICP-OES spectrometer may be used.

In some embodiments, the first liquid stream contains the dissolved saltin an amount of at least about 1 wt %, at least about 5 wt %, at leastabout 10 wt %, at least about 15 wt %, at least about 20 wt %, at leastabout 25 wt %, at least about 26 wt %, at least about 27 wt %, at leastabout 28 wt %, at least about 29 wt %, or at least about 30 wt %(and/or, in certain embodiments, up to the solubility limit of thedissolved salt in the first liquid stream). In some embodiments, thefirst liquid stream comprises the dissolved salt in an amount in therange of about 1 wt % to about 30 wt %, about 5 wt % to about 30 wt %,about 10 wt % to about 30 wt %, about 15 wt % to about 30 wt %, about 20wt % to about 30 wt %, about 25 wt % to about 30 wt %, about 26 wt % toabout 30 wt %, about 27 wt % to about 30 wt %, about 28 wt % to about 30wt %, or about 29 wt % to about 30 wt %.

The heating device may be any device that is capable of transferringheat to a fluid stream. In some embodiments, the heating devicecomprises a first liquid inlet and a first liquid outlet. In certaincases, the heating device comprises a first fluidic pathway. The firstliquid inlet of the heating device may be a liquid inlet of the firstfluidic pathway, and the first liquid outlet of the heating device maybe a liquid outlet of the first fluidic pathway. In some embodiments,the first liquid inlet of the heating device is fluidically connected toa source of a first liquid stream comprising a condensable fluid inliquid phase and a dissolved salt. In some embodiments, the first liquidinlet of the heating device comprises or is fluidically connected to anintermediate humidifier liquid outlet of the humidifier. In certainembodiments, the first liquid outlet of the first heating devicecomprises or is fluidically connected to a main liquid inlet of thehumidifier.

In some embodiments, the heating device is a heat exchanger. The heatingdevice may be any type of heat exchanger known in the art. In somecases, the heat exchanger comprises a first fluidic pathway and a secondfluidic pathway. A first fluid stream may flow through the first fluidicpathway, and a second fluid stream may flow through the second fluidicpathway. The first fluid stream and the second fluid stream may be indirect or indirect contact, and heat may be transferred between thefirst fluid stream and the second fluid stream. In some embodiments, thefirst fluid stream and the second fluid stream are only in indirectcontact. In certain embodiments, the second fluid stream comprises aheating fluid. The heating fluid may be any fluid capable of absorbingand transferring heat. Non-limiting examples of suitable heating fluidsinclude water, air, saturated/superheated steam, synthetic organic-basednon-aqueous fluids, glycol, brines, and/or mineral oils.

In some embodiments, a first fluid stream flows through the firstfluidic pathway in a first direction, and a second fluid stream flowsthrough the second fluidic pathway in a second direction that issubstantially opposite from the first direction (e.g., counter flow),substantially the same as the first direction (e.g., parallel flow), orsubstantially perpendicular to the first direction (e.g., cross flow).In certain cases, a counter-flow heat exchanger may be more efficientthan other types of heat exchangers. In some embodiments, the heatingdevice is a counter-flow heat exchanger. In some embodiments, more thantwo fluid streams may flow through the heat exchanger.

In some embodiments, the first fluid stream flowing through the firstfluidic pathway of the heating device and/or the second fluid streamflowing through the second fluidic pathway of the heating device areliquid streams, and the heating device is a liquid-to-liquid heatexchanger. In other embodiments, the first fluid stream flowing throughthe first fluidic pathway of the heating device and/or the second fluidstream flowing through the second fluidic pathway of the heating deviceare gas streams. In some embodiments, the first fluid stream and/orsecond fluid stream do not undergo a phase change (e.g., liquid to gasor vice versa) within the heating device.

Examples of suitable heat exchangers include, but are not limited to,plate-and-frame heat exchangers, shell-and-tube heat exchangers,tube-and-tube heat exchangers, plate heat exchangers, plate-and-shellheat exchangers, and the like. In a particular, non-limiting embodiment,the heating device is a plate-and-frame heat exchanger.

In some embodiments, the heat exchanger may exhibit relatively high heattransfer rates. In some embodiments, the heat exchanger may have a heattransfer coefficient of at least about 150 W/(m² K), at least about 200W/(m² K), at least about 500 W/(m² K), at least about 1000 W/(m² K), atleast about 2000 W/(m² K), at least about 3000 W/(m² K), at least about4000 W/(m² K), at least about 5000 W/(m² K), at least about 6000 W/(m²K), at least about 7000 W/(m² K), at least about 8000 W/(m² K), at leastabout 9000 W/(m² K), or at least about 10,000 W/(m² K). In someembodiments, the heat exchanger may have a heat transfer coefficient inthe range of about 150 W/(m² K) to about 10,000 W/(m² K), about 200W/(m² K) to about 10,000 W/(m² K), about 500 W/(m² K) to about 10,000W/(m² K), about 1000 W/(m² K) to about 10,000 W/(m² K), about 2000 W/(m²K) to about 10,000 W/(m² K), about 3000 W/(m² K) to about 10,000 W/(m²K), about 4000 W/(m² K) to about 10,000 W/(m² K), about 5000 W/(m² K) toabout 10,000 W/(m² K), about 6000 W/(m² K) to about 10,000 W/(m² K),about 7000 W/(m² K) to about 10,000 W/(m² K), about 8000 W/(m² K) toabout 10,000 W/(m² K), or about 9000 W/(m² K) to about 10,000 W/(m² K).

In some embodiments, the heating device is a heat collection device. Theheat collection device may be configured to produce and/or store and/orutilize thermal energy (e.g., in the form of combustion of natural gas,solar energy, waste heat from a power plant, or waste heat fromcombusted exhaust). In certain cases, the heating device is configuredto convert electrical energy to thermal energy. For example, the heatingdevice may be an electric heater. In some embodiments, the heatingdevice comprises a furnace (e.g., a combustion furnace).

The heating device may, in some cases, increase the temperature of oneor more fluid streams flowing through (or otherwise in contact with) theheating device. For example, the difference between the temperature of afluid stream entering the heating device and the fluid stream exitingthe heating device may be at least about 5° C., at least about 10° C.,at least about 15° C., at least about 20° C., at least about 30° C., atleast about 40° C., or at least about 50° C. In some embodiments, thedifference between the temperature of a fluid stream entering theheating device and the fluid stream exiting the heating device may be inthe range of about 5° C. to about 10° C., about 5° C. to about 15° C.,about 5° C. to about 20° C., about 5° C. to about 30° C., about 5° C. toabout 40° C., about 5 ° C. to about 50° C., about 10° C. to about 20°C., about 10° C. to about 30° C., about 10° C. to about 40° C., about10° C. to about 50° C., about 20° C. to about 30° C., about 20° C. toabout 40° C., or about 20° C. to about 50° C. In some cases, thetemperature of a fluid stream (e.g., a first fluid stream) being heatedin the heating device remains below the boiling point of the fluidstream.

In some embodiments, the first heating device utilizes low-grade heat(e.g., heat having a temperature of about 90° C. or less) to increasethe temperature of the fluid stream. In certain cases, for example,low-grade heat may be obtained from industrial processes, cogenerationplants, geothermal heat sources, solar radiation, combustion engines(e.g., diesel generator cooling jackets), power plant cooling water, oilrefineries, metallurgy processes (e.g., titanium refining), and/orconventional heat sources.

The humidifier may be any type of humidifier known in the art. In someembodiments, the humidifier is configured to receive a liquid streamcomprising a condensable fluid in liquid phase and a dissolved salt(e.g., a heated first liquid stream received from the heating device).In some embodiments, the humidifier is also configured to receive a gasstream via at least one humidifier gas inlet (e.g., a main humidifiergas inlet, an intermediate humidifier gas inlet). In some cases, the gascomprises at least one non-condensable gas. A non-condensable gasgenerally refers to a gas that cannot be condensed from gas phase toliquid phase under the operating conditions of the humidifier. Examplesof suitable non-condensable gases include, but are not limited to, air,nitrogen, oxygen, helium, argon, carbon monoxide, carbon dioxide, sulfuroxides (SO_(x)) (e.g., SO₂, SO₃), nitrogen oxides (NO_(x)) (e.g., NO,NO₂), and/or a combination thereof. In some embodiments, the gas is agas mixture (e.g., the gas comprises at least one non-condensable gasand one or more additional gases).

In the humidifier, the gas stream may come into contact (e.g., direct orindirect contact) with the heated first liquid stream exiting theheating device. In some embodiments, the temperature of the heated firstliquid stream is higher than the temperature of the gas stream.

According to some embodiments, upon contact of the gas stream and theheated first liquid stream within the humidifier, an amount of heat andat least a portion of the condensable fluid in the liquid aretransferred from the heated first liquid stream to the gas stream via anevaporation (e.g., humidification) process, thereby producing avapor-containing humidifier gas outlet stream and a cooled, concentratedliquid stream. In some embodiments, the vapor-containing humidifier gasoutlet stream comprises a vapor mixture (e.g., a mixture of thecondensable fluid in vapor phase and the non-condensable gas). Incertain cases, the condensable fluid is water, and the vapor-containinghumidifier gas outlet stream is enriched in water vapor relative to thegas stream received from the main humidifier gas inlet. In someembodiments, the cooled, concentrated liquid stream has a higherconcentration of the dissolved salt than the heated first liquid stream(e.g., the cooled, concentrated liquid stream is enriched in thedissolved salt relative to the heated first liquid stream).

In some embodiments, the humidifier is configured such that a mainliquid inlet is positioned at a first end (e.g., a top end) of thehumidifier, and a main gas inlet is positioned at a second, opposite end(e.g., a bottom end) of the humidifier. The humidifier may also comprisea main liquid outlet at the second end of the humidifier and a main gasoutlet at the first end of the humidifier. Such a configuration mayfacilitate the flow of a liquid stream (e.g., the heated first liquidstream) in a first direction through the humidifier from the main liquidinlet to the main liquid outlet and the flow of a gas stream in asecond, substantially opposite direction through the humidifier from themain gas inlet to the main gas outlet, which may advantageously resultin high thermal efficiency. In addition, the humidifier may comprise atleast one intermediate humidifier liquid outlet and/or at least oneintermediate humidifier liquid inlet. In certain embodiments, thehumidifier may further comprise at least one intermediate humidifier gasoutlet and/or at least one intermediate humidifier gas inlet.

In certain embodiments, the humidifier comprises a plurality of stages(e.g., the humidifier is a multi-stage humidifier). In some embodiments,the plurality of stages comprises a first stage, a last stage, and oneor more intermediate stages positioned between the first stage and thelast stage. As used herein, the first humidifier stage refers to thefirst stage of the humidifier encountered by a liquid stream enteringthe humidifier through the main liquid inlet. The first humidifier stageis, therefore, generally the stage of the humidifier positioned inclosest proximity to the main humidifier liquid inlet. In someembodiments, the first humidifier stage comprises or is fluidicallyconnected (e.g., directly fluidically connected) to the main humidifierliquid inlet (e.g., the main humidifier liquid inlet is a liquid inletof the first humidifier stage). As used herein, the last humidifierstage refers to the last stage of the humidifier encountered by a liquidstream flowing through the humidifier. The last humidifier stage is,therefore, generally the stage of the humidifier positioned in closestproximity to the main humidifier liquid outlet. In some embodiments, thelast humidifier stage comprises or is fluidically connected (e.g.,directly fluidically connected) to the main humidifier liquid outlet(e.g., the main humidifier liquid outlet is a liquid outlet of the lasthumidifier stage). In some embodiments, in addition to the mainhumidifier liquid outlet fluidically connected to the last humidifierstage, the humidifier may comprise an intermediate humidifier liquidoutlet. As used herein, an intermediate humidifier liquid outlet refersto a liquid outlet of the first stage or one of the one or moreintermediate stages of the plurality of stages of the humidifier. In thehumidifier, the plurality of stages may be vertically arranged (e.g.,the first stage may be positioned above the last stage) or horizontallyarranged (e.g., the first stage may be positioned to the left or rightof the last stage).

The humidifier may have any number of stages. In some embodiments, thehumidifier has at least one, at least two, at least three, at leastfour, at least five, at least six, at least seven, at least eight, atleast nine, or at least ten or more stages. In some embodiments, thehumidifier has 1-10 stages, 2-10 stages, 3-10 stages, 4-10 stages, 5-10stages, 6-10 stages, 7-10 stages, 8-10 stages, or 9-10 stages. In someembodiments, the stage are arranged such that they are substantiallyparallel to each other. In certain cases, the stages are positioned atan angle.

In some embodiments, the humidifier further comprises a gas distributionchamber positioned between the main humidifier gas inlet and theplurality of stages. In certain embodiments, such as those embodimentsin which the humidifier comprises a plurality of vertically-arrangedstages, the gas distribution chamber is positioned at or near the bottomportion of the humidifier. In some embodiments, the gas distributionchamber comprises or is fluidically connected (e.g., directlyfluidically connected) to the main humidifier gas inlet. The gasdistribution chamber may have sufficient volume to allow a gas stream(e.g., a gas stream comprising a non-condensable gas) to substantiallyevenly diffuse over the cross section of the humidifier.

In some cases, the gas distribution chamber further comprises a liquidlayer (e.g., a liquid sump volume). For example, liquid (e.g.,comprising the condensable fluid in liquid phase and a dissolved salt)may collect in the liquid sump volume after exiting the last stage ofthe humidifier. In some cases, the liquid sump volume comprises or isfluidically connected (e.g., directly fluidically connected) to the mainhumidifier liquid outlet of the humidifier. In certain embodiments, theliquid sump volume is in fluid communication with a pump that pumpsliquid out of the humidifier. The liquid sump volume may, for example,provide a positive suction pressure on the intake of the pump, and mayadvantageously prevent negative (e.g., vacuum) suction pressure thatcould induce deleterious cavitation bubbles. In some cases, the liquidsump volume may advantageously decrease the sensitivity of thehumidifier to changes in flow rate, salinity, temperature, and/or heattransfer rate.

According to some embodiments, the humidifier is configured tofacilitate direct contact between a liquid stream and a gas stream. Insome embodiments, the humidifier is a bubble column humidifier. As notedabove, a bubble column humidifier may be associated with certainadvantages over other types of humidifiers, such as increased thermalefficiency. In some embodiments, at least one stage of the bubble columnhumidifier comprises a bubble generator. In certain embodiments, thebubble generator may act as a gas inlet for the at least one stage. Inoperation, the at least one stage of the bubble column humidifier mayfurther comprise a liquid layer comprising an amount of a condensablefluid in liquid phase and a dissolved salt (e.g., at least a portion ofa heated first liquid stream).

In some embodiments, the at least one stage may further comprise a vapordistribution region positioned adjacent the liquid layer (e.g., abovethe liquid layer). The vapor distribution region refers to the spacewithin the stage throughout which vapor is distributed (e.g., theportion of the stage not occupied by the liquid layer). The vapordistribution region may, in certain cases, advantageously damp out flowvariations created by random bubbling by allowing a gas to redistributeevenly across the cross section of the humidifier. Additionally, in thefree space of the vapor distribution region, large droplets entrained inthe gas may have some space to fall back into the liquid layer beforethe gas enters the subsequent stage. In some embodiments, the vapordistribution region is positioned between two liquid layers of twoconsecutive stages. The vapor distribution region may serve to separatethe two consecutive stages, thereby increasing the thermodynamiceffectiveness of the humidifier by keeping the liquid layers of eachstage separate. In some embodiments, each stage of a plurality of stagesof the bubble column humidifier comprises a bubble generator, a liquidlayer, and a vapor distribution region positioned adjacent the liquidlayer.

In some embodiments, a humidifier gas inlet stream (e.g., a gas streamcomprising a non-condensable gas) enters the bubble column humidifierthrough a main humidifier gas inlet, and a humidifier liquid inletstream (e.g., a heated first liquid stream) enters the bubble columnhumidifier through a main humidifier liquid inlet. The humidifier gasinlet stream may flow through the bubble generator of the at least onestage of the humidifier, thereby forming a plurality of gas bubbles. Insome cases, the gas bubbles flow through the liquid layer of the atleast one stage of the humidifier. As the gas bubbles directly contactthe liquid layer, which may have a higher temperature than the gasbubbles, heat and/or mass (e.g., the condensable fluid) may betransferred from the liquid layer to the gas bubbles through anevaporation (e.g., humidification) process, thereby forming a heated, atleast partially humidified humidifier gas outlet stream (e.g., avapor-containing humidifier gas outlet stream) and a humidifier liquidoutlet stream (e.g., a cooled, concentrated liquid stream) having ahigher concentration of the dissolved salt than the humidifier liquidinlet stream. In certain embodiments, the condensable fluid is water,and the humidifier gas outlet stream is enriched in water vapor relativeto the humidifier gas inlet stream received from the main humidifier gasinlet. In some embodiments, bubbles of the heated, at least partiallyhumidified gas exit the liquid layer and recombine in the vapordistribution region, and the heated, at least partially humidified gasis substantially evenly distributed throughout the vapor distributionregion. The vapor-containing humidifier gas outlet stream may exit thebubble column humidifier through the main humidifier gas outlet, and thehumidifier liquid outlet stream may exit the bubble column humidifierthrough the main humidifier liquid outlet.

In some embodiments, the bubble column humidifier comprises a pluralityof stages, and one or more stages of the plurality of stages comprise aliquid layer comprising an amount of a condensable fluid in liquid phaseand a dissolved salt (e.g., at least a portion of a heated first liquidstream). In some embodiments relating to multi-stage bubble columnhumidifiers, the temperature of a liquid layer of a first stage (e.g.,the topmost stage in a vertically arranged humidifier) may be higherthan the temperature of a liquid layer of a second stage (e.g., a stagepositioned below the first stage in a vertically arranged humidifier),which may be higher than the temperature of a liquid layer of a thirdstage (e.g., a stage positioned below the second stage in a verticallyarranged humidifier). In some embodiments, each stage in a multi-stagebubble column humidifier operates at a temperature below that of theprevious stage (e.g., the stage above it, in embodiments comprisingvertically arranged humidifiers).

The presence of multiple stages within the bubble column humidifier may,in some cases, advantageously result in increased humidification of agas stream. For example, the presence of multiple stages may providenumerous locations where the gas may be humidified. That is, the gas maytravel through more than one liquid layer in which at least a portion ofthe gas undergoes evaporation (e.g., humidification). In addition, thepresence of multiple stages within the bubble column humidifier mayadvantageously enable greater flexibility for fluid flow (e.g.,extraction and/or injection of liquid streams and/or gas streams fromintermediate humidifier stages).

It should be noted that the inventive systems and methods describedherein are not limited to those including a bubble column humidifier andthat other types of humidifiers may be used in some embodiments. Forexample, in certain embodiments, the humidifier is a packed bedhumidifier. In certain cases, the humidifier comprises a packingmaterial (e.g., polyvinyl chloride (PVC) packing material). The packingmaterial may, in some cases, facilitate turbulent gas flow and/orenhanced direct contact between the liquid stream comprising acondensable fluid in liquid phase and at least one dissolved salt andthe gas stream within the humidifier. In certain embodiments, thehumidifier further comprises a device configured to produce droplets ofthe liquid stream. For example, a nozzle or other spraying device may bepositioned at the top of the humidifier such that the liquid stream issprayed downward to the bottom of the humidifier. The use of a sprayingdevice can advantageously increase the degree of contact between theliquid stream fed to the humidifier and the gas stream into which waterfrom the liquid stream is transported.

In some embodiments, the humidifier (e.g., the bubble column humidifier)is configured to have a relatively high evaporation rate. In certaincases, for example, the humidifier has an evaporation rate of at leastabout 500 barrels/day, at least about 600 barrels/day, at least about700 barrels/day, at least about 800 barrels/day, at least about 900barrels/day, at least about 1,000 barrels a day, at least about 1,100barrels/day, at least about 1,200 barrels/day, at least about 1,300barrels/day, at least about 1,400 barrels/day, at least about 1,500barrels/day, at least about 2,000 barrels/day, at least about 3,000barrels/day, at least about 4,000 barrels/day, or at least about 5,000barrels/day. In some embodiments, the humidifier has an evaporation rateof about 500 barrels/day to about 5,000 barrels/day, about 600barrels/day to about 5,000 barrels/day, about 700 barrels/day to about5,000 barrels/day, about 800 barrels/day to about 5,000 barrels/day,about 900 barrels/day to about 5,000 barrels/day, about 1,000barrels/day to about 5,000 barrels/day, about 1,100 barrels/day to about5,000 barrels/day, about 1,200 barrels/day to about 5,000 barrels/day,about 1,300 barrels/day to about 5,000 barrels/day, about 1,400barrels/day to about 5,000 barrels/day, about 1,500 barrels/day to about5,000 barrels/day, about 2,000 barrels/day to about 5,000 barrels/day,about 3,000 barrels/day to about 5,000 barrels/day, or about 4,000barrels/day to about 5,000 barrels/day. The evaporation rate of thehumidifier may be obtained by measuring the total liquid output volumeof the humidifier (e.g., the volume of all humidifier liquid outletstreams) over a time period (e.g., one day) and subtracting the inputvolume of the humidifier (e.g., the volume of all humidifier liquidinlet streams, such as the heated first liquid stream) over the sametime period.

According to some embodiments, the humidifier liquid outlet stream has arelatively high concentration of the dissolved salt. In certainembodiments, the concentration of the dissolved salt (e.g., NaCl) in thehumidifier liquid outlet stream is at least about 1,000 mg/L, at leastabout 5,000 mg/L, at least about 10,000 mg/L, at least about 50,000mg/L, at least about 100,000 mg/L, at least about 150,000 mg/L, at leastabout 200,000 mg/L, at least about 250,000 mg/L, at least about 300,000mg/L, at least about 350,000 mg/L, at least about 400,000 mg/L, at leastabout 450,000 mg/L, or at least about 500,000 mg/L (and/or, in certainembodiments, up to the solubility limit of the dissolved salt in theliquid stream). In some embodiments, the concentration of the dissolvedsalt in the humidifier liquid outlet stream is in the range of about1,000 mg/L to about 10,000 mg/L, about 1,000 mg/L to about 50,000 mg/L,about 1,000 mg/L to about 100,000 mg/L, about 1,000 mg/L to about150,000 mg/L, about 1,000 mg/L to about 200,000 mg/L, about 1,000 mg/Lto about 250,000 mg/L, about 1,000 mg/L to about 300,000 mg/L, about1,000 mg/L to about 350,000 mg/L, about 1,000 mg/L to about 400,000mg/L, about 1,000 mg/L to about 450,000 mg/L, about 1,000 mg/L to about500,000 mg/L, about 10,000 mg/L to about 50,000 mg/L, about 10,000 mg/Lto about 100,000 mg/L, about 10,000 mg/L to about 150,000 mg/L, about10,000 mg/L to about 200,000 mg/L, about 10,000 mg/L to about 250,000mg/L, about 10,000 mg/L to about 300,000 mg/L, about 10,000 mg/L toabout 350,000 mg/L, about 10,000 mg/L to about 400,000 mg/L, about10,000 mg/L to about 450,000 mg/L, about 10,000 mg/L to about 500,000mg/L, about 50,000 mg/L to about 100,000 mg/L, about 50,000 mg/L toabout 150,000 mg/L, about 50,000 mg/L to about 200,000 mg/L, about50,000 mg/L to about 250,000 mg/L, about 50,000 mg/L to about 300,000mg/L, about 50,000 mg/L to about 350,000 mg/L, about 50,000 mg/L toabout 400,000 mg/L, about 50,000 mg/L to about 450,000 mg/L, about50,000 mg/L to about 500,000 mg/L, about 100,000 mg/L to about 150,000mg/L, about 100,000 mg/L to about 200,000 mg/L, about 100,000 mg/L toabout 250,000 mg/L, about 100,000 mg/L to about 300,000 mg/L, about100,000 mg/L to about 350,000 mg/L, about 100,000 mg/L to about 400,000mg/L, about 100,000 mg/L to about 450,000 mg/L, or about 100,000 mg/L toabout 500,000 mg/L.

In some embodiments, the humidifier liquid outlet stream contains thedissolved salt in an amount of at least about 1 wt %, at least about 5wt %, at least about 10 wt %, at least about 15 wt %, at least about 20wt %, at least about 25 wt %, at least about 26 wt %, at least about 27wt %, at least about 28 wt %, at least about 29 wt %, or at least about30 wt % (and/or, in certain embodiments, up to the solubility limit ofthe dissolved salt in the humidifier liquid outlet stream). In someembodiments, the humidifier liquid outlet stream comprises the dissolvedsalt in an amount in the range of about 1 wt % to about 30 wt %, about 5wt % to about 30 wt %, about 10 wt % to about 30 wt %, about 15 wt % toabout 30 wt %, about 20 wt % to about 30 wt %, about 25 wt % to about 30wt %, about 26 wt % to about 30 wt %, about 27 wt % to about 30 wt %,about 28 wt % to about 30 wt %, or about 29 wt % to about 30 wt %.

In some embodiments, the concentration of the dissolved salt in thehumidifier liquid outlet stream is substantially greater than theconcentration of the dissolved salt in the humidifier liquid inletstream (e.g., heated first liquid stream). In some cases, theconcentration of the dissolved salt in the humidifier liquid outletstream is at least about 0.5%, about 1%, about 2%, about 5%, about 10%,about 15%, or about 20% greater than the concentration of the dissolvedsalt in the humidifier liquid inlet stream.

In some embodiments, the system further comprises a dehumidifier (e.g.,a bubble column condenser) fluidically connected to the humidifier. FIG.2 illustrates an exemplary system comprising a dehumidifier. As shown inFIG. 2, system 200 comprises humidifier 202, heating device 204, anddehumidifier 240. Humidifier 202 comprises a plurality of stagescomprising first stage 202A, last stage 202E, and intermediate stages202B-202D positioned between first stage 202A and last stage 202E.Dehumidifier 240 comprises a plurality of stages comprising first stage240A, last stage 240E, and intermediate stages 240B-240D positionedbetween first stage 240A and last stage 240E. A main humidifier gasoutlet 234 of humidifier 202 may be fluidically connected to a maindehumidifier gas inlet 258 of dehumidifier 240. Optionally, anintermediate gas outlet 236 of humidifier 202 may be fluidicallyconnected to an intermediate dehumidifier gas inlet 254 of dehumidifier240. For example, FIG. 2 shows intermediate humidifier stage 202C asbeing fluidically connected to intermediate dehumidifier stage 240C. Itshould be noted, however, that if humidifier 202 comprises anintermediate gas outlet, the intermediate gas outlet of humidifier 202may be a gas outlet of any intermediate stage of humidifier 202 (e.g.,any one of intermediate stages 202B-202D), and if dehumidifier 240comprises an intermediate gas inlet, the intermediate gas inlet ofdehumidifier 240 may be a gas inlet of any intermediate stage ofdehumidifier 240 (e.g., any one of intermediate stages 240B-240D). Inaddition, a main dehumidifier gas outlet 250 of dehumidifier 240 mayoptionally be fluidically connected to a main humidifier gas inlet 232of humidifier 202 (fluidic connection not shown in FIG. 2). A firstliquid inlet 222 of heating device 204 may be fluidically connected toan intermediate humidifier liquid outlet 228 of humidifier 202 and/or amain humidifier liquid outlet 230 of humidifier 202. A first liquidoutlet 224 of heating device 204 may be fluidically connected to a mainhumidifier liquid inlet 226 of humidifier 202.

In operation, humidifier 202 and heating device 204 may be operatedsimilarly to humidifier 102 and heating device 104, which were describedin relation to FIG. 1. In addition, vapor-containing humidifier gasoutlet stream 214 may be directed to flow to dehumidifier 240 and mayenter dehumidifier 240 through main dehumidifier gas inlet 258fluidically connected to last dehumidifier stage 240E. In certainembodiments, a partially humidified gas stream 238 may also be directedto flow from intermediate humidifier gas outlet 236 fluidicallyconnected to an intermediate humidifier stage (e.g., intermediatehumidifier stage 202C) to intermediate dehumidifier gas inlet 254fluidically connected to an intermediate dehumidifier stage (e.g.,intermediate dehumidifier stage 240C). A condensable liquid stream 224comprising an amount of the condensable fluid in liquid phase may enterdehumidifier 240 through main dehumidifier liquid inlet 252 fluidicallyconnected to first dehumidifier stage 240A. Condensable liquid stream244 may flow in a first direction through dehumidifier 240 from firststage 240A to last stage 240E, and vapor-containing humidifier gasoutlet stream 214 may flow through dehumidifier 240 in a seconddirection through dehumidifier 240 from last stage 240E to first stage240A. Within dehumidifier 240, heat and mass may be transferred fromvapor-containing humidifier gas outlet stream 214 to condensable liquidstream 244 (e.g., through a condensation process), thereby producing acooled, at least partially dehumidified gas stream and an amount ofheated condensable liquid that is added to condensable liquid stream244. Condensable liquid stream 244 may exit dehumidifier 240 throughmain dehumidifier liquid outlet 256 as dehumidifier liquid outlet stream246. In some cases, at least a portion 248 of dehumidifier liquid outletstream 246 is discharged from system 200. In some cases, at least aportion 244 of dehumidifier liquid outlet stream 246 is returned todehumidifier 240 through main dehumidifier liquid inlet 252. The cooled,at least partially dehumidified gas stream may exit dehumidifier 240through main dehumidifier gas outlet 260 as dehumidifier gas outletstream 250. In some cases, at least a portion of dehumidifier gas outletstream 250 may be discharged from system 200 (e.g., by being vented intothe atmosphere as waste exhaust). In some cases, at least a portion ofdehumidifier gas outlet stream 250 is directed to flow to main gas inlet232 of humidifier 202 (fluidic connection not shown in FIG. 2).

The dehumidifier may be any type of dehumidifier known in the art. Insome embodiments, the dehumidifier is configured to receive avapor-containing humidifier gas outlet stream (e.g., a heated, at leastpartially humidified gas stream) as a dehumidifier gas inlet stream. Thedehumidifier may also be configured to receive a condensable liquidstream (e.g., a liquid stream comprising the condensable fluid in liquidphase) as a dehumidifier liquid inlet stream. In some embodiments, thedehumidifier liquid inlet stream comprises water. In certain cases, thedehumidifier liquid inlet stream comprises substantially pure water(e.g., water having a relatively low dissolved salt concentration).

In the dehumidifier, the dehumidifier gas inlet stream (e.g., thevapor-containing humidifier gas outlet stream) may come into contact(e.g., direct or indirect contact) with the dehumidifier liquid inletstream (e.g., the condensable liquid stream). The dehumidifier gas inletstream may have a higher temperature than the dehumidifier liquid inletstream, and upon contact of the dehumidifier gas inlet stream and thedehumidifier liquid inlet stream, heat and/or mass may be transferredfrom the dehumidifier gas inlet stream to the dehumidifier liquid inletstream. In certain embodiments, the dehumidifier gas inlet streamcomprises the condensable fluid in vapor phase and a non-condensablegas, and at least a portion of the condensable fluid is transferred fromthe dehumidifier gas inlet stream to the dehumidifier liquid inletstream via a condensation (e.g., dehumidification) process, therebyproducing a dehumidifier liquid outlet stream comprising the condensablefluid in liquid phase and an at least partially dehumidifieddehumidifier gas outlet stream. In certain cases, the condensable fluidis water, and the dehumidifier gas outlet stream is lean in water vaporrelative to the dehumidifier gas inlet stream (e.g., thevapor-containing humidifier gas outlet stream). In some embodiments, thedehumidifier liquid outlet stream comprises substantially pure water. Incertain cases, the dehumidifier liquid outlet stream comprises water inthe amount of at least about 95 wt %, at least about 99 wt %, at leastabout 99.9 wt %, or at least about 99.99 wt % (and/or, in certainembodiments, up to about 99.999 wt %, or more).

In some embodiments, the dehumidifier is configured such that a mainliquid inlet is positioned at a first end (e.g., a top end) of thedehumidifier, and a main gas inlet is positioned at a second, oppositeend (e.g., a bottom end) of the dehumidifier. The dehumidifier may alsocomprise a main liquid outlet at the second end of the dehumidifier anda main gas outlet at the first end of the dehumidifier. Such aconfiguration may facilitate the flow of a liquid stream (e.g., thedehumidifier liquid inlet stream) in a first direction through thedehumidifier from the main liquid inlet to the main liquid outlet andthe flow of a gas stream (e.g., the vapor-containing humidifier gasoutlet stream) in a second, substantially opposite direction through thedehumidifier from the main gas inlet to the main gas outlet, which mayadvantageously result in high thermal efficiency. In addition, thedehumidifier may comprise at least one intermediate dehumidifier liquidoutlet and/or at least one intermediate dehumidifier liquid inlet. Incertain embodiments, the dehumidifier may further comprise at least oneintermediate dehumidifier gas outlet and/or at least one intermediatedehumidifier gas inlet.

In certain embodiments, the dehumidifier comprises a plurality of stages(e.g., the dehumidifier is a multi-stage dehumidifier). In someembodiments, the plurality of stages comprises a first stage, a laststage, and one or more intermediate stages positioned between the firststage and the last stage. As used herein, the first dehumidifier stagerefers to the first stage of the dehumidifier encountered by a liquidstream entering the dehumidifier through the main liquid inlet. Thefirst dehumidifier stage is, therefore, generally the stage of thedehumidifier positioned in closest proximity to the main dehumidifierliquid inlet. In some embodiments, the first dehumidifier stage isfluidically connected (e.g., directly fluidically connected) to the maindehumidifier liquid inlet (e.g., the main dehumidifier liquid inlet is aliquid inlet of the first dehumidifier stage). As used herein, the lastdehumidifier stage refers to the last stage of the dehumidifierencountered by a liquid stream flowing through the dehumidifier. Thelast dehumidifier stage is, therefore, generally the stage of thedehumidifier positioned in closest proximity to the main dehumidifierliquid outlet. In some embodiments, the last dehumidifier stage isfluidically connected (e.g., directly fluidically connected) to the maindehumidifier liquid outlet (e.g., the main dehumidifier liquid outlet isa liquid outlet of the last dehumidifier stage).

In some embodiments, in addition to the main dehumidifier liquid outletfluidically connected to the last humidifier stage, the dehumidifier maycomprise an intermediate dehumidifier liquid outlet. As used herein, anintermediate dehumidifier liquid outlet refers to a liquid outlet of thefirst stage or one of the one or more intermediate stages of theplurality of stages of the dehumidifier. In the dehumidifier, theplurality of stages may be vertically arranged (e.g., the first stagemay be positioned above the last stage) or horizontally arranged (e.g.,the first stage may be positioned to the left or right of the laststage).

The dehumidifier may have any number of stages. In some embodiments, thedehumidifier has at least one, at least two, at least three, at leastfour, at least five, at least six, at least seven, at least eight, atleast nine, or at least ten or more stages. In some embodiments, thedehumidifier has 1-10 stages, 2-10 stages, 3-10 stages, 4-10 stages,5-10 stages, 6-10 stages, 7-10 stages, 8-10 stages, or 9-10 stages. Insome embodiments, the stages are arranged such that they aresubstantially parallel to each other. In certain cases, the stages arepositioned at an angle.

In some embodiments, the dehumidifier further comprises a gasdistribution chamber positioned between the main dehumidifier gas inletand the plurality of stages. In certain embodiments, such as thoseembodiments in which the dehumidifier comprises a plurality ofvertically-arranged stages, the gas distribution chamber is positionedat or near the bottom portion of the dehumidifier. In some embodiments,the gas distribution chamber is fluidically connected (e.g., directlyfluidically connected) to the main dehumidifier gas inlet. The gasdistribution chamber may have sufficient volume to allow a gas stream(e.g., a vapor-containing humidifier gas outlet stream) to substantiallyevenly diffuse over the cross section of the dehumidifier.

In some cases, the gas distribution chamber further comprises a liquidlayer (e.g., a liquid sump volume). For example, liquid (e.g.,comprising the condensable fluid in liquid phase) may collect in theliquid sump volume after exiting the last stage of the dehumidifier. Insome cases, the liquid sump volume is fluidically connected (e.g.,directly fluidically connected) to the main dehumidifier liquid outletof the dehumidifier. In certain embodiments, the liquid sump volume isin fluid communication with a pump that pumps liquid out of thedehumidifier. The liquid sump volume may, for example, provide apositive suction pressure on the intake of the pump, and mayadvantageously prevent negative (e.g., vacuum) suction pressure thatcould induce deleterious cavitation bubbles. In some cases, the liquidsump volume may advantageously decrease the sensitivity of thedehumidifier to changes in flow rate, salinity, temperature, and/or heattransfer rate.

According to some embodiments, the dehumidifier is configured tofacilitate direct contact between a liquid stream and a gas stream. Insome embodiments, the dehumidifier is a bubble column condenser. Asnoted above, a bubble column condenser may be associated with certainadvantages over other types of dehumidifiers, such as increased thermalefficiency. In some embodiments, at least one stage of the bubble columncondenser comprises a bubble generator. In certain embodiments, thebubble generator may act as a gas inlet for the at least one stage. Inoperation, the at least one stage of the bubble column condenser mayfurther comprise a liquid layer comprising an amount of a condensablefluid in liquid phase (e.g., at least a portion of a condensable liquidstream).

In some embodiments, the at least one stage may further comprise a vapordistribution region positioned adjacent the liquid layer (e.g., abovethe liquid layer). The vapor distribution region refers to the spacewithin the stage throughout which vapor is distributed (e.g., theportion of the stage not occupied by the liquid layer). The vapordistribution region may, in certain cases, advantageously damp out flowvariations created by random bubbling by allowing a gas to redistributeevenly across the cross section of the dehumidifier. Additionally, inthe free space of the vapor distribution region, large dropletsentrained in the gas may have some space to fall back into the liquidlayer before the gas enters the subsequent stage. In some embodiments,the vapor distribution region is positioned between two liquid layers oftwo consecutive stages. The vapor distribution region may serve toseparate the two consecutive stages, thereby increasing thethermodynamic effectiveness of the bubble column condenser by keepingthe liquid layers of each stage separate. In some embodiments, eachstage of a plurality of stages of the bubble column condenser comprisesa bubble generator, a liquid layer, and a vapor distribution regionpositioned adjacent the liquid layer.

In some embodiments, the bubble column condenser is configured toreceive a vapor-containing humidifier gas outlet stream (e.g.,comprising a heated, at least partially humidified gas) through a maindehumidifier gas inlet as a dehumidifier gas inlet stream. Thedehumidifier gas inlet stream may flow through the bubble generator ofthe at least one stage of the condenser, thereby forming a plurality ofbubbles of the heated, at least partially humidified gas. In some cases,the gas bubbles flow through the liquid layer of the at least one stageof the condenser. As the gas bubbles directly contact the liquid layer,which may have a lower temperature than the gas bubbles, heat and/ormass (e.g., condensable fluid) may be transferred from the gas bubblesto the liquid layer via a condensation (e.g., dehumidification) process,thereby forming a cooled, at least partially dehumidified dehumidifiergas outlet stream and a dehumidifier liquid outlet stream comprising thecondensable fluid in liquid phase. In certain embodiments, thecondensable fluid is water, and the dehumidifier gas outlet stream islean in water vapor relative to the dehumidifier gas inlet streamreceived from the main dehumidifier gas inlet. In some embodiments,bubbles of the cooled, at least partially dehumidified gas exit theliquid layer and recombine in the vapor distribution region, and thecooled, at least partially dehumidified gas is substantially evenlydistributed throughout the vapor distribution region. The dehumidifiergas outlet stream may exit the bubble column condenser through the maindehumidifier gas outlet, and the dehumidifier liquid outlet stream mayexit the bubble column condenser through the main dehumidifier liquidoutlet.

In embodiments, the bubble column condenser comprises a plurality ofstages, and one or more stages of the plurality of stages comprise aliquid layer comprising an amount of a condensable fluid in liquidphase. In some embodiments relating to multi-stage dehumidifiers, thetemperature of a liquid layer of a first stage (e.g., the topmost stagein a vertically arranged dehumidifier) may be lower than the temperatureof a liquid layer of a second stage (e.g., a stage positioned below thefirst stage in a vertically arranged dehumidifier), which may be lowerthan the temperature of a liquid layer of a third stage (e.g., a stagepositioned below the second stage in a vertically arrangeddehumidifier). In some embodiments, each stage in a multi-stagedehumidifier operates at a temperature above that of the previous stage(e.g., the stage above it, in embodiments comprising vertically arrangeddehumidifiers).

The presence of multiple stages within the bubble column condenser may,in some cases, advantageously result in increased dehumidification of agas stream. In some cases, the presence of multiple stages mayadvantageously lead to higher recovery of a condensable fluid in liquidphase. For example, the presence of multiple stages may provide numerouslocations where the gas may be dehumidified (e.g., treated to recoverthe condensable liquid). That is, the gas may travel through more thanone liquid layer in which at least a portion of the gas undergoesdehumidification (e.g., condensation). In addition, the presence ofmultiple stages may increase the difference in temperature between aliquid stream at an inlet and an outlet of a dehumidifier. For example,the use of multiple stages can produce a dehumidifier liquid outletstream having increased temperature relative to the dehumidifier liquidinlet stream. This may be advantageous in systems where heat from aliquid stream (e.g., dehumidifier liquid outlet stream) is transferredto a separate stream (e.g., humidifier liquid inlet stream) within thesystem. In such cases, the ability to produce a heated dehumidifierliquid outlet stream can increase the energy effectiveness of thesystem. Additionally, the presence of multiple stages may enable greaterflexibility for fluid flow within a system (e.g., extraction and/orinjection of liquid streams and/or gas streams from intermediatedehumidifier stages).

It should be noted that the inventive systems and methods describedherein are not limited to those including a bubble column condenser andthat other types of dehumidifiers may be used in some embodiments. Forexample, the dehumidifier may be a surface condenser, a spray tower, ora packed bed tower. In certain cases, the dehumidifier may comprise asurface (e.g., a metal surface) in contact with a gas stream comprisinga condensable fluid in vapor phase.

In some embodiments, the dehumidifier (e.g., bubble column condenser) isconfigured to have a relatively high condensation rate. In certaincases, for example, the dehumidifier has a condensation rate of at leastabout 500 barrels/day, at least about 600 barrels/day, at least about700 barrels/day, at least about 800 barrels/day, at least about 900barrels/day, at least about 1,000 barrels a day, at least about 1,100barrels/day, at least about 1,200 barrels/day, at least about 1,300barrels/day, at least about 1,400 barrels/day, at least about 1,500barrels/day, at least about 2,000 barrels/day, at least about 3,000barrels/day, at least about 4,000 barrels/day, or at least about 5,000barrels/day. In some embodiments, the dehumidifier has a condensationrate of about 500 barrels/day to about 5,000 barrels/day, about 600barrels/day to about 5,000 barrels/day, about 700 barrels/day to about5,000 barrels/day, about 800 barrels/day to about 5,000 barrels/day,about 900 barrels/day to about 5,000 barrels/day, about 1,000barrels/day to about 5,000 barrels/day, about 1,100 barrels/day to about5,000 barrels/day, about 1,200 barrels/day to about 5,000 barrels/day,about 1,300 barrels/day to about 5,000 barrels/day, about 1,400barrels/day to about 5,000 barrels/day, about 1,500 barrels/day to about5,000 barrels/day, about 2,000 barrels/day to about 5,000 barrels/day,about 3,000 barrels/day to about 5,000 barrels/day, or about 4,000barrels/day to about 5,000 barrels/day. The condensation rate of thedehumidifier may be obtained by measuring the total liquid output volumeof the dehumidifier (e.g., the volume of all dehumidifier liquid outletstreams) over a time period (e.g., one day) and subtracting the inputvolume of the dehumidifier (e.g., the volume of all dehumidifier liquidinlet streams) over the time period. According to some embodiments, thedehumidifier liquid outlet stream has a relatively low concentration ofthe dissolved salt. In certain embodiments, the concentration of thedissolved salt in the dehumidifier liquid outlet stream is about 500mg/L or less, about 200 mg/L or less, about 100 mg/L or less, about 50mg/L or less, about 20 mg/L or less, about 10 mg/L or less, about 5 mg/Lor less, about 2 mg/L or less, about 1 mg/L or less, about 0.5 mg/L orless, about 0.2 mg/L or less, about 0.1 mg/L or less, about 0.05 mg/L orless, about 0.02 mg/L or less, or about 0.01 mg/L or less. In somecases, the concentration of the dissolved salt in the dehumidifierliquid outlet stream is substantially zero (e.g., not detectable). Incertain cases, the concentration of the dissolved salt in thedehumidifier liquid outlet stream is in the range of about 0 mg/L toabout 500 mg/L, about 0 mg/L to about 200 mg/L, about 0 mg/L to about100 mg/L, about 0 mg/L to about 50 mg/L, about 0 mg/L to about 20 mg/L,about 0 mg/L to about 10 mg/L, about 0 mg/L to about 5 mg/L, about 0mg/L to about 2 mg/L, about 0 mg/L to about 1 mg/L, about 0 mg/L toabout 0.5 mg/L, about 0 mg/L to about 0.1 mg/L, about 0 mg/L to about0.05 mg/L, about 0 mg/L to about 0.02 mg/L, or about 0 mg/L to about0.01 mg/L.

In some embodiments, the dehumidifier liquid outlet stream contains thedissolved salt in an amount of about 2 wt % or less, about 1 wt % orless, about 0.5 wt % or less, about 0.2 wt % or less, about 0.1 wt % orless, about 0.05 wt % or less, or about 0.01 wt % or less. In someembodiments, the dehumidifier liquid outlet stream contains thedissolved salt in an amount in the range of about 0.01 wt % to about 2wt %, about 0.01 wt % to about 1 wt %, about 0.01 wt % to about 0.5 wt%, about 0.01 wt % to about 0.2 wt %, or about 0.01 wt % to about 0.1 wt%.

In some embodiments, the concentration of the dissolved salt in thedehumidifier liquid outlet stream is substantially less than theconcentration of the dissolved salt in the first liquid stream receivedby the system. In some cases, the concentration of the dissolved salt inthe dehumidifier liquid outlet stream is at least about 0.5%, about 1%,about 2%, about 5%, about 10%, about 15%, or about 20% less than theconcentration of the dissolved salt in the first liquid stream.

In some embodiments, the system (e.g., HDH system) has a relatively highproduction rate (e.g., amount of substantially pure water produced perunit time). In certain cases, the system has a production rate of atleast about 500 barrels/day, at least about 600 barrels/day, at leastabout 700 barrels/day, at least about 800 barrels/day, at least about900 barrels/day, at least about 1,000 barrels a day, at least about1,100 barrels/day, at least about 1,200 barrels/day, at least about1,300 barrels/day, at least about 1,400 barrels/day, at least about1,500 barrels/day, at least about 2,000 barrels/day, at least about3,000 barrels/day, at least about 4,000 barrels/day, or at least about5,000 barrels/day. In some embodiments, the system has a production ratein the range of about 500 barrels/day to about 5,000 barrels/day, about600 barrels/day to about 5,000 barrels/day, about 700 barrels/day toabout 5,000 barrels/day, about 800 barrels/day to about 5,000barrels/day, about 900 barrels/day to about 5,000 barrels/day, about1,000 barrels/day to about 5,000 barrels/day, about 1,100 barrels/day toabout 5,000 barrels/day, about 1,200 barrels/day to about 5,000barrels/day, about 1,300 barrels/day to about 5,000 barrels/day, about1,400 barrels/day to about 5,000 barrels/day, about 1,500 barrels/day toabout 5,000 barrels/day, about 2,000 barrels/day to about 5,000barrels/day, about 3,000 barrels/day to about 5,000 barrels/day, orabout 4,000 barrels/day to about 5,000 barrels/day.

In some embodiments, the system further comprises a second heatingdevice, which may be in the form of a heat exchanger. In certain cases,the second heating device/heat exchanger facilitates transfer of heatfrom a fluid stream exiting the dehumidifier (e.g., a dehumidifierliquid outlet stream) to a fluid stream entering the system (e.g., afirst liquid stream) and/or a fluid stream recirculating through thesystem. For example, the second heating device/heat exchanger mayadvantageously allow energy to be recovered from a dehumidifier liquidoutlet stream and be used to pre-heat an influent liquid stream prior toentry of the influent liquid stream into the heating device or thehumidifier. The presence of the second heating device/heat exchanger torecover energy from the dehumidifier liquid outlet stream may,therefore, reduce the amount of heat required to be applied to theinfluent liquid stream. In some embodiments, the system can beconfigured such that the cooled dehumidifier liquid outlet stream can bereturned to the dehumidifier through a main dehumidifier liquid inletand be re-used as a liquid to form liquid layers in one or more stagesof the dehumidifier.

FIG. 3A is a schematic diagram of an exemplary system comprising asecond heat exchanger 362. In FIG. 3A, system 300 comprises humidifier302, first heating device/heat exchanger 304, dehumidifier 340, andsecond heat exchanger 362. In addition, system 300 comprises optionalfirst tank 364 and optional second tank 366. Humidifier 302 comprises aplurality of stages 302A-302E, and dehumidifier 340 comprises aplurality of stages 340A-340E.

In some cases, a flow path for a gas stream encompasses humidifier 302and dehumidifier 340. A main humidifier gas outlet 334 of humidifier 302is fluidically connected to a main dehumidifier gas inlet 358 ofdehumidifier 340. In addition, a main dehumidifier gas outlet 360 ofdehumidifier 340 is, optionally, fluidically connected to a mainhumidifier gas inlet 332 of humidifier 302.

In some cases, a main flow path for a liquid stream comprising acondensable fluid in liquid phase and a dissolved salt encompassessecond heat exchanger 332, first heating device/heat exchanger 304,humidifier 302, and optional second tank 336. A first liquid inlet 368of second heat exchanger 362 is fluidically connected to a source of afirst liquid stream 306 comprising a condensable fluid in liquid phaseand a dissolved salt. A first liquid outlet 370 of second heat exchanger332 is fluidically connected to a first liquid inlet 322 of firstheating device/heat exchanger 304. A first liquid outlet 324 of firstheating device/heat exchanger 304 is fluidically connected to a mainhumidifier liquid inlet 326 of humidifier 302. A main humidifier liquidoutlet 330 of humidifier 302 is fluidically connected to optional secondtank 336, which is also fluidically connected to first liquid inlet 368of second heat exchanger 362.

In some cases, a fluidic circuit for a recirculated liquid streamcomprising a condensable fluid in liquid phase and a dissolved saltencompasses first heating device/heat exchanger 304, humidifier 302, andoptional first tank 364. First liquid outlet 324 of first heatingdevice/heat exchanger 304 is fluidically connected to main humidifierliquid inlet 326 of humidifier 302. Intermediate humidifier liquidoutlet 328 of humidifier 302 is fluidically connected to optional firsttank 364, which is fluidically connected to first liquid inlet 322 ofheating device 304.

In some cases, a main flow path for a liquid stream comprising acondensable fluid in liquid phase encompasses dehumidifier 340 andsecond heat exchanger 332. Main dehumidifier liquid outlet 346 isfluidically connected to second liquid inlet 374 (e.g., a liquid inletof a second fluidic pathway) of second heat exchanger 362. Second liquidoutlet 374 of second heat exchanger 332 is fluidically connected to maindehumidifier liquid inlet 352 of dehumidifier 340.

In operation, first liquid stream 306 may enter second heat exchanger362. Heat may be transferred from dehumidifier liquid outlet stream 346to first liquid stream 306 to form pre-heated first liquid stream 376.Pre-heated first liquid stream 376 may exit heat exchanger 362 and becombined with at least a portion of one or more additional liquidstreams (e.g., extracted liquid stream 310 exiting intermediatehumidifier liquid outlet 328) to form combined stream 378. In someembodiments, the difference between the temperature of extracted liquidstream 310 and the temperature of pre-heated first liquid stream 376 maybe relatively small (e.g., about 10° C. or less). Combined stream 378may then enter first heating device/heat exchanger 304 through firstliquid inlet 322. Within first heating device/heat exchanger 304,combined stream 378 may be heated to form heated combined stream 308.Heated combined stream 308 may enter first stage 302A of humidifier 302through main humidifier liquid inlet 326.

A gas stream 312 may enter humidifier 302 through main humidifier gasinlet 332, which is fluidically connected to last stage 302E ofhumidifier 302. As gas stream 312 flows through humidifier 302 from laststage 302E to first stage 302A, heated combined stream 308 maysimultaneously flow through humidifier 302 from first stage 302A to laststage 302E.

In first stage 302A of humidifier 302, heat and mass may be transferredfrom heated combined stream 308 to gas stream 312 (e.g., through anevaporation process), thereby forming a cooled, concentrated liquidstream and a heated, at least partially humidified gas stream. In somecases, the heated, at least partially humidified gas stream may exithumidifier 302 through main humidifier gas outlet 334 asvapor-containing humidifier gas outlet stream 314. In some cases, atleast a portion of the cooled, concentrated liquid stream exitshumidifier 302 through intermediate humidifier liquid outlet 328 asextracted liquid stream 310. As shown in FIG. 3A, extracted liquidstream 310 may be directed to flow to optional first tank 364. Fromoptional first tank 364, at least a portion of extracted liquid stream310 may then be combined with pre-heated first liquid stream 376 to formcombined stream 378, which may be directed to flow to first liquid inlet322 of first heating device/heat exchanger 304. Combined stream 378 maybe heated within first heating device/heat exchanger 304 to produceheated combined stream 308, which may be directed to enter humidifier302 through main humidifier gas inlet 326.

A liquid stream may recirculate through the fluidic circuit formed byfirst liquid inlet 322 of first heating device/heat exchanger 304, firstliquid outlet 324 of first heating device/heat exchanger 304, mainhumidifier liquid inlet 326 of humidifier 302, intermediate humidifierliquid outlet 328 of humidifier 302, and optional first tank 364. Insome cases, optional first tank 364 may provide the fluidic circuit witha thermal, physical, and concentrative buffer volume. In someembodiments, amounts of liquid may be added or removed (e.g., to controlthe salinity of the liquid stream recirculated through the fluidiccircuit), for example by adjusting (e.g., increasing or decreasing)extraction and/or injection flow rates at various points throughout thefluidic circuit. In some cases, liquid replacement in the fluidiccircuit may be substantially continuous, discontinuous (e.g., batch), orsemi-discontinuous (e.g., semi-batch).

The remaining portion of the cooled, concentrated liquid stream thatdoes not exit humidifier 302 through intermediate humidifier liquidoutlet 328 as extracted liquid stream 310 may flow through the remainderof humidifier 302 and become further cooled and concentrated as gasstream 312 becomes correspondingly further heated and humidified. Thecooled, concentrated liquid stream may exit humidifier 302 as humidifierliquid outlet stream 316.

In some cases, at least a portion 318 of humidifier liquid outlet stream316 may be discharged from system 300. Portion 318 of humidifier liquidoutlet stream 316 may be discharged in order, for example, to maintain asteady state system salinity. In some cases, all of humidifier liquidoutlet stream 316 may be discharged from system 300. In certain cases,any remaining portion of humidifier liquid outlet stream 316 may flow tooptional second tank 366. In some cases, the presence of optional secondtank 366 in system 300 may reduce salinity and temperature fluctuationsduring regular operation due to providing additional system volume. Insome cases, an additional influent stream 382 comprising the condensablefluid in liquid phase and a dissolved salt may enter optional secondtank 366 (e.g., as a make-up stream). In some cases, a stream 320comprising a remaining portion of humidifier liquid outlet stream 316and/or a portion of additional influent stream 382 may be directed toflow from optional second tank 366 to first liquid inlet 368 of secondheat exchanger 362.

After flowing through humidifier 302, the heated, humidified gas streammay exit humidifier 302 through main humidifier gas outlet 334 asvapor-containing humidifier gas outlet stream 314. Stream 314 may bedirected to flow to main dehumidifier gas inlet 358 of dehumidifier 340.Stream 314 may flow through dehumidifier 340 in a direction from laststage 340E to first stage 340A, and condensable liquid stream 344 maysimultaneously flow through dehumidifier 340 in a direction from firststage 340A to last stage 340E. As streams 314 and 344 flow throughdehumidifier 340, heat and mass may be transferred from vapor-containinghumidifier gas outlet stream 314 to condensable liquid stream 344 (e.g.,through a condensation process), thereby forming a cooled, at leastpartially dehumidified gas stream. In addition, as condensable fluidcondenses from vapor-containing humidifier gas outlet stream 314,amounts of heated condensable liquid may be added to condensable liquidstream 344.

The cooled, at least partially dehumidified gas stream may exitdehumidifier 340 through main dehumidifier gas outlet 360 asdehumidifier gas outlet stream 350. In some embodiments, at least aportion of dehumidifier gas outlet stream 350 is discharged from system300 (e.g., vented into the environment as waste heat exhaust). In someembodiments, at least a portion of dehumidifier gas outlet stream 350 isdirected to flow to main humidifier gas inlet 332 of humidifier 302.

The heated condensable liquid stream may exit dehumidifier 340 asdehumidifier liquid outlet stream 346. As shown in FIG. 3A, dehumidifierliquid outlet stream 346 may be directed to flow to second heatexchanger 362. In second heat exchanger 362, first liquid stream 306 mayflow through a first fluidic pathway and dehumidifier liquid outletstream 346 may flow through a second fluidic pathway, and heat may betransferred from dehumidifier liquid outlet stream 346 to first liquidstream 306. After flowing through the second fluidic pathway of heatexchanger 362, the cooled dehumidifier liquid outlet stream may exitsecond heat exchanger 362 as cooled stream 380. In some embodiments, atleast a portion 348 of cooled stream 380 is discharged from system 300.In some embodiments, at least a portion of cooled stream 380 is returnedto dehumidifier 340 as condensable liquid stream 344.

In the system illustrated in FIG. 3A, some overlap exists between thefluidic circuit for the recirculated liquid stream (first heatingdevice/heat exchanger 304, the portion of humidifier 302 between mainhumidifier liquid inlet 326 and intermediate humidifier liquid outlet328, and optional first tank 364 in FIG. 3A) and the humidifier mainflow path for the liquid stream comprising a condensable fluid in liquidphase and a dissolved salt (humidifier 302 from first humidifier stage302A to last humidifier stage 302E, optional second tank 366, secondheat exchanger 362, and first heating device/heat exchanger 304). Inparticular, both the recirculated liquid stream fluidic circuit and thehumidifier main flow path include first liquid inlet 322 of firstheating device/heat exchanger 304, first liquid outlet 324 of firstheating device/heat exchanger 304, and main humidifier liquid inlet 326of humidifier 302. In some embodiments, however, the recirculated liquidstream fluidic circuit and the humidifier main flow path are at leastpartially separated/isolated (e.g., such that humidifier liquid outletstream 316 is not recirculated through all or any parts of therecirculated liquid stream fluidic circuit—see FIG. 3B). In certaincases, at least partially separating the recirculated liquid streamfluidic circuit and the humidifier main flow path may advantageouslyfacilitate temperature and/or flow control. FIG. 3B is a schematicdiagram of an exemplary system in which the fluidic circuit and the mainflow path are separated.

System 300 in FIG. 3B comprises the same components (e.g., humidifier302, dehumidifier 340, first heating device/heat exchanger 304, secondheat exchanger 362) as in FIG. 3A. However, in system 300 of FIG. 3B,first liquid outlet 368 of second heat exchanger 362 is fluidicallyconnected to intermediate humidifier liquid inlet 382 of stage 302B ofhumidifier 302 instead of first liquid inlet 322 of first heatingdevice/heat exchanger 304. Intermediate humidifier liquid inlet 382 maybe any liquid inlet of any one or more of the one or more intermediatestages of humidifier 302. As shown in FIG. 3B, the fluidic circuitthrough which a liquid stream recirculates comprises first liquid inlet322 of first heating device/heat exchanger 304, first liquid outlet 324of first heating device/heat exchanger 304, main humidifier liquid inlet326 of humidifier 302, intermediate humidifier liquid outlet 328 ofhumidifier 302, and optional first tank 364. In contrast, the humidifiermain flow path comprises first liquid inlet 368 of second heat exchanger362, first liquid outlet 370 of second heat exchanger 362, intermediatehumidifier liquid inlet 382 of humidifier 302, main humidifier liquidoutlet 330 of humidifier 302, and optional second tank 366.

In operation, first liquid stream 306 may enter second heat exchanger362 through first liquid inlet 368. As first liquid stream 306 flowsthrough a first fluidic pathway of second heat exchanger 362,dehumidifier liquid outlet stream 346 may flow through a second fluidicpathway of second heat exchanger 362, and heat may be transferred fromdehumidifier liquid outlet stream 346 to first liquid stream 306 to formpre-heated first liquid stream 376. Pre-heated first liquid stream 376may then be directed to flow to intermediate liquid inlet 382 ofhumidifier 302 (e.g., a liquid inlet of intermediate humidifier stage302B or 302C). After entering humidifier 302 through intermediate liquidinlet 382, pre-heated first liquid stream 376 may flow throughhumidifier 302 as previously described in relation to FIG. 3A.

Separately, an influent liquid stream comprising a condensable fluid inliquid phase and a dissolved salt may be introduced into first heatingdevice/heat exchanger 304, and the influent stream may be heated toproduce heated influent stream 308. Heated influent stream 308 may enterfirst stage 302A of humidifier 302 through main humidifier liquid inlet326. In first stage 302A, heat and mass may be transferred from heatedinfluent stream 308 to gas stream 312, thereby producing a cooled,concentrated liquid stream and a heated, at least partially humidifiedgas stream. The heated, at least partially humidified gas stream mayexit humidifier 302 through main humidifier gas outlet 334 asvapor-containing humidifier gas outlet stream 314, which may be directedto flow to main dehumidifier gas inlet 358 of dehumidifier 340. At leasta portion of the cooled, concentrated liquid stream may exit humidifier302 as extracted liquid stream 310. In some cases, extracted liquidstream 310 may be directed to flow to optional first tank 364. Fromoptional first tank 364, extracted liquid stream 310 may be returned tofirst heating device/heat exchanger 304.

In some embodiments, an amount of liquid may be added to or removed fromthe fluidic circuit. In some cases, for example, additional liquid maybe added at an average rate approximately equal to the evaporation ratein first humidifier stage 302A. In certain cases, pre-heated firstliquid stream 376 may be a source of the additional liquid. In someembodiments, an additional influent stream comprising the condensablefluid in liquid phase and a dissolved salt (not shown in FIG. 3B) mayenter optional first tank 364 (e.g., as a make-up stream). In someembodiments, an amount of concentrated liquid may be removed from thefluidic circuit and replaced with liquid having a lower concentration ofthe dissolved salt (e.g., in order to control the salinity of therecirculated liquid stream). In some cases, the replacement may becontinuous, discontinuous (e.g., batch), or semi-discontinuous (e.g.,semi-batch).

The second heat exchanger (e.g., heat exchanger 362 in FIGS. 3A-3B) maybe any type of heat exchanger known in the art. In some embodiments, thesecond heat exchanger comprises a first fluidic pathway and a secondfluidic pathway, each comprising an inlet (e.g., a liquid inlet) and anoutlet (e.g., a liquid outlet). As used herein, the first inlet andfirst outlet of the second heat exchanger refer to the inlet and outletof the first fluidic pathway, respectively, and the second inlet andsecond outlet of the second heat exchanger refer to the inlet and outletof the second fluidic pathway, respectively. In some embodiments, afirst fluid stream may flow through the first fluidic pathway, and asecond fluid stream may flow through the second fluidic pathway. Thefirst fluid stream and the second fluid stream may be in direct orindirect contact, and heat may be transferred between the first fluidstream and the second fluid stream. In some embodiments, the first fluidstream and the second fluid stream are only in indirect contact.

In some embodiments, a first fluid stream flows through the firstfluidic pathway in a first direction, and a second fluid stream flowsthrough the second fluidic pathway in a second direction that issubstantially opposite from the first direction (e.g., counter flow),substantially the same as the first direction (e.g., parallel flow), orsubstantially perpendicular to the first direction (e.g., cross flow).In certain cases, a counter-flow heat exchanger may be more efficientthan other types of heat exchangers. In some embodiments, the secondheat exchanger is a counter-flow heat exchanger. In some embodiments,more than two fluid streams may flow through the second heat exchanger.

In some embodiments, the first fluid stream flowing through the firstfluidic pathway of the second heat exchanger and/or the second fluidstream flowing through the second fluidic pathway of the second heatexchanger are liquid streams. In certain embodiments, the heating deviceis a liquid-to-liquid heat exchanger. In some embodiments, the firstfluid stream and/or second fluid stream do not undergo a phase change(e.g., liquid to gas) within the second heat exchanger. In certainembodiments, the first fluid stream is an influent liquid streamentering the system (e.g., a first liquid stream), and the second fluidstream is a liquid stream exiting the dehumidifier (e.g., a dehumidifierliquid outlet stream).

Examples of suitable heat exchangers include, but are not limited to,plate-and-frame heat exchangers, shell-and-tube heat exchangers,tube-and-tube heat exchangers, plate heat exchangers, plate-and-shellheat exchangers, spiral heat exchangers, and the like. In a particularembodiment, the heat exchanger is a plate-and-frame heat exchanger. Anon-limiting example of a suitable commercially available heat exchangeris Plate Concepts Modu-Flex Plate & Frame Product #MFL041D1PA150-115.

In some embodiments, the second heat exchanger may exhibit relativelyhigh heat transfer rates. In some embodiments, the second heat exchangermay have a heat transfer coefficient of at least about 150 W/(m² K), atleast about 200 W/(m² K), at least about 500 W/(m² K), at least about1000 W/(m² K), at least about 2000 W/(m² K), at least about 3000 W/(m²K), at least about 4000 W/(m² K), or, in some cases, at least about 5000W/(m² K), at least about 6000 W/(m² K), at least about 7000 W/(m² K), atleast about 8000 W/(m² K), at least about 9000 W/(m² K), or at leastabout 10,000 W/(m² K). In some embodiments, the second heat exchangermay have a heat transfer coefficient in the range of about 150 W/(m² K)to about 10,000 W/(m² K), about 200 W/(m² K) to about 10,000 W/(m² K),about 500 W/(m² K) to about 10,000 W/(m² K), about 1000 W/(m² K) toabout 10,000 W/(m² K), about 2000 W/(m² K) to about 10,000 W/(m² K),about 3000 W/(m² K) to about 10,000 W/(m² K), or about 4000 W/(m² K) toabout 10,000 W/(m² K), about 5000 W/(m² K) to about 10,000 W/(m² K),about 6000 W/(m² K) to about 10,000 W/(m² K), about 7000 W/(m² K) toabout 10,000 W/(m² K), about 8000 W/(m² K) to about 10,000 W/(m² K), orabout 9000 W/(m² K) to about 10,000 W/(m² K).

The second heat exchanger may, in some cases, increase the temperatureof one or more fluid streams flowing through the second heat exchanger.For example, the difference between the temperature of a fluid streamentering the second heat exchanger and the fluid stream exiting thesecond heat exchanger may be at least about 5 ° C., at least about 10 °C., at least about 15° C., at least about 20° C., at least about 30° C.,at least about 40° C., or at least about 50° C. In some embodiments, thedifference between the temperature of a fluid stream entering the secondheat exchanger and the fluid stream exiting the second heat exchangermay be in the range of about 5° C. to about 10° C., about 5° C. to about15° C., about 5° C. to about 20° C., about 5° C. to about 30° C., about5° C. to about 40° C., about 5 ° C. to about 50° C., about 10° C. toabout 20° C., about 10° C. to about 30° C., about 10° C. to about 40°C., about 10° C. to about 50° C., about 20° C. to about 30° C., about20° C. to about 40° C., or about 20° C. to about 50° C. In some cases,the temperature of a fluid stream (e.g., a first liquid stream) beingheated in the second heat exchanger remains below the boiling point ofthe fluid stream.

In some embodiments, the second heat exchanger is an external heatexchanger (e.g., external to the humidifier and dehumidifier). In somecases, an external heat exchanger may be associated with certainadvantages. For example, the use of an external heat exchanger with ahumidifier and/or dehumidifier may advantageously allow the humidifierand/or dehumidifier to have reduced dimensions and/or reduced liquidlayer heights within one or more stages.

In some embodiments, the second heat exchanger is an internal heatexchanger (e.g., internal to the humidifier or dehumidifier). Forexample, an internal heat exchanger may comprise a tube coil locatedwithin the dehumidifier. The tube coil may be positioned such that atleast a portion of the tube coil is in thermal contact with a liquidlayer within a stage of the dehumidifier. For example, in a dehumidifier(e.g., bubble column condenser) comprising a plurality of stages, eachstage comprising a liquid layer, the tube coil may be positioned suchthat each liquid layer is in thermal contact with at least a portion ofthe tube coil. In some cases, a coolant (e.g., an influent liquidstream) may flow through the internal heat exchanger (e.g., the tubecoil), and heat may be transferred from the liquid layer(s) of thedehumidifier to the coolant.

In some embodiments, the system further comprises an optional firsttank. In certain embodiments, the optional first tank is fluidicallyconnected (e.g., directly fluidically connected) to an intermediatehumidifier liquid outlet. In certain embodiments, the optional firsttank is fluidically connected (e.g., directly fluidically connected) tothe first liquid inlet of the heating device. In some cases, theoptional first tank forms part of a fluidic circuit through which aliquid stream (e.g., a stream comprising a condensable fluid in liquidphase and a dissolved salt) is recirculated. The optional first tank mayprovide the fluidic circuit with thermal, physical, and/or concentrativebuffer volume, thereby reducing fluctuations (e.g., salinity and/ortemperature fluctuations) during operation.

In some embodiments, the system further comprises an optional secondtank. In certain embodiments, the optional second tank is fluidicallyconnected (e.g., directly fluidically connected) to the main humidifierliquid outlet. In certain embodiments, the optional second tank isfluidically connected (e.g., directly fluidically connected) to thefirst liquid inlet of the heating device and/or the first liquid inletof the second heat exchanger. In some cases, the optional second tankmay increase system volume and provide the main flow path with thermal,physical, and/or concentrative buffer volume, thereby reducingfluctuations (e.g., salinity and/or temperature fluctuations) duringoperation.

The first tank and second tank may be any type of tank known in the artand may comprise any vessel capable of holding a volume of a liquid. Thefirst tank and second tank may also have any size. In some embodiments,the first tank and/or second tank have a volume of at least about 100gallons, at least about 250 gallons, at least about 500 gallons, atleast about 750 gallons, at least about 1,000 gallons, at least about2,000 gallons, at least about 5,000 gallons, or at least about 10,000gallons. In some embodiments, the first tank and/or second tank have avolume in the range of about 100 gallons to about 250 gallons, about 100gallons to about 500 gallons, about 100 gallons to about 750 gallons,about 100 gallons to about 1,000 gallons, about 100 gallons to about2,000 gallons, about 100 gallons to about 5,000 gallons, or about 100gallons to about 10,000 gallons.

As noted above, the humidifier may be a bubble column humidifier and/orthe dehumidifier may be a bubble column condenser. Accordingly, thehumidifier and/or dehumidifier may comprise one or more bubblegenerators. The one or more bubble generators may have various features(e.g., holes) used for generation of bubbles. The selection of a bubblegenerator can affect the size and/or shape of the gas bubbles generated,thereby affecting heat and/or mass transfer between gas bubbles and aliquid layer of a humidifier or a dehumidifier. Appropriate bubblegenerator and/or bubble generator conditions (e.g., bubble generatorspeeds) may be selected to produce a particular desired set of gasbubbles. Non-limiting examples of suitable bubble generators include asparger plate (e.g., a plate comprising a plurality of holes throughwhich a gas can travel), a device comprising one or more perforatedpipes (e.g., having a radial, annular, spider-web, or hub-and-spokeconfiguration), a device comprising one or more nozzles, porous media(e.g., microporous metal), and/or a device comprising bubble caps.

In certain embodiments, a bubble generator comprises a sparger plate. Ithas been recognized that a sparger plate may have certain advantageouscharacteristics. For example, the pressure drop across a sparger platemay be relatively low. Additionally, the simplicity of the sparger platemay render it inexpensive to manufacture and/or resistant to the effectsof fouling. According to some embodiments, the sparger plate comprises aplurality of holes, at least a portion of which have a diameter (ormaximum cross-sectional dimension for non-circular holes) in the rangeof about 0.1 mm to about 50 mm, about 0.1 mm to about 25 mm, about 0.1mm to about 15 mm, about 0.1 mm to about 10 mm, about 0.1 mm to about 5mm, about 0.1 mm to about 1 mm, about 1 mm to about 50 mm, about 1 mm toabout 25 mm, about 1 mm to about 15 mm, about 1 mm to about 10 mm, orabout 1 mm to about 5 mm. In certain embodiments, substantially all theholes of the plurality of holes have a diameter (or maximumcross-sectional dimension) in the range of about 0.1 mm to about 50 mm,about 0.1 mm to about 25 mm, about 0.1 mm to about 15 mm, about 0.1 mmto about 10 mm, about 0.1 mm to about 5 mm, about 0.1 mm to about 1 mm,about 1 mm to about 50 mm, about 1 mm to about 25 mm, about 1 mm toabout 15 mm, about 1 mm to about 10 mm, or about 1 mm to about 5 mm. Theholes may have any suitable shape. For example, at least a portion ofthe plurality of holes may be substantially circular, substantiallyelliptical, substantially square, substantially rectangular,substantially triangular, and/or irregularly shaped. In someembodiments, substantially all the holes of the plurality of holes aresubstantially circular, substantially elliptical, substantially square,substantially rectangular, substantially triangular, and/or irregularlyshaped.

In some cases, the sparger plate may be arranged along the bottomsurface of a stage within the humidifier and/or the dehumidifier. Insome embodiments, the sparger plate may have a surface area that coversat least about 50%, at least about 60%, at least about 70%, at leastabout 80%, at least about 90%, at least about 95%, or about 100% of across-section of the humidifier and/or the dehumidifier.

In some cases, inlets and/or outlets within the humidifier and/ordehumidifier may be provided as separate and distinct structuralelements/features. In some cases, inlets and/or outlets within thehumidifier and/or dehumidifier may be provided by certain componentssuch as the bubble generator and/or any other features that establishfluid communication between components of the humidifier and/ordehumidifier. For example, the “gas inlet” and/or “gas outlet” of ahumidifier or a dehumidifier may be provided as a plurality of holes ofa bubble generator (e.g., a sparger plate). In some embodiments, atleast one bubble generator is coupled to a gas inlet of a stage of thehumidifier and/or the dehumidifier. In some embodiments, a bubblegenerator is coupled to a gas inlet of each stage of the humidifierand/or dehumidifier.

In addition to one or more bubble generators, one or more stages of thehumidifier (e.g., bubble column humidifier) and/or dehumidifier (e.g.,bubble column condenser) may comprise a liquid layer. In some cases, thecomposition of a liquid layer in a stage of the humidifier may bedifferent from the composition of a liquid layer in a stage of thedehumidifier. For example, in the humidifier, the liquid layer maycomprise a liquid comprising a condensable fluid in liquid phase and adissolved salt. In the dehumidifier, the liquid layer may comprise thecondensable fluid in liquid phase (e.g., water). In certain embodiments,a liquid layer of the dehumidifier comprises the condensable fluid inliquid phase in substantially purified form (e.g., having a relativelylow level of contaminants, including dissolved salts). According to someembodiments, a liquid layer of the dehumidifier comprises substantiallypure water.

In some embodiments, the height of the liquid layer in one or morestages of the humidifier and/or dehumidifier is relatively low duringoperation of the system (e.g., substantially continuous operation and/orsubstantially transient operation). In some cases, the height of aliquid layer within a stage can be measured vertically from the surfaceof the bubble generator that contacts the liquid layer to the topsurface of the liquid layer. Having a relatively low liquid layer heightin at least one stage of the humidifier and/or dehumidifier may, in someembodiments, advantageously result in a relatively low pressure dropbetween the inlet and outlet of an individual stage. Without wishing tobe bound by a particular theory, the pressure drop across a given stageof the humidifier or dehumidifier may be due, at least in part, to thehydrostatic head of the liquid in the stage that the gas has toovercome. In addition, having a relatively low liquid layer height in atleast one stage of the humidifier and/or dehumidifier may, in someembodiments, advantageously enhance heat and/or mass transfer. Withoutwishing to be bound by a particular theory, the theoretical maximumamount of heat and/or mass transfer in the humidifier and/ordehumidifier may occur under conditions where the gas reaches the sametemperature as the liquid and the amount of vapor in the gas is exactlyat the saturation concentration. The liquid layer height may determinehow close the heat and/or mass transfer gets to the aforementionedtheoretical maximum, although above a minimum liquid layer height theperformance may be unaffected. Therefore, it may be advantageous tomaintain the liquid layer height at the minimum required to operate thesystem without affecting performance.

In some embodiments, during operation of the humidifier and/ordehumidifier (e.g., substantially continuous operation and/orsubstantially transient operation), the liquid layer within at least onestage of the humidifier and/or dehumidifier has a height of about 0.1 mor less, about 0.09 m or less, about 0.08 m or less, about 0.07 m orless, about 0.06 m or less, about 0.05 m or less, about 0.04 m or less,about 0.03 m or less, about 0.02 m or less, about 0.01 m or less, or, insome cases, about 0.005 m or less. In some embodiments, during operationof the humidifier and/or dehumidifier, the liquid layer within at leastone stage of the humidifier and/or dehumidifier has a height in therange of about 0 m to about 0.1 m, about 0 m to about 0.09 m, about 0 mto about 0.08 m, about 0 m to about 0.07 m, about 0 m to about 0.06 m,about 0 m to about 0.05 m, about 0 m to about 0.04 m, about 0 m to about0.03 m, about 0 m to about 0.02 m, about 0 m to about 0.01 m, about 0 mto about 0.005 m, about 0.005 m to about 0.1 m, about 0.005 m to about0.09 m, about 0.005 m to about 0.08 m, about 0.005 m to about 0.07 m,about 0.005 m to about 0.06 m, about 0.005 m to about 0.05 m, about0.005 m to about 0.04 m, about 0.005 m to about 0.03 m, about 0.005 m toabout 0.02 m, or about 0.005 m to about 0.01 m.

In some embodiments, during operation of the humidifier and/ordehumidifier (e.g., substantially continuous operation and/orsubstantially transient operation), the liquid layer within each stageof the humidifier and/or dehumidifier has a height of about 0.1 m orless, about 0.09 m or less, about 0.08 m or less, about 0.07 m or less,about 0.06 m or less, about 0.05 m or less, about 0.04 m or less, about0.03 m or less, about 0.02 m or less, about 0.01 m or less, or, in somecases, about 0.005 m or less. In some embodiments, during operation ofthe humidifier and/or dehumidifier, the liquid layer within each stageof the humidifier and/or dehumidifier has a height in the range of about0 m to about 0.1 m, about 0 m to about 0.09 m, about 0 m to about 0.08m, about 0 m to about 0.07 m, about 0 m to about 0.06 m, about 0 m toabout 0.05 m, about 0 m to about 0.04 m, about 0 m to about 0.03 m,about 0 m to about 0.02 m, about 0 m to about 0.01 m, about 0 m to about0.005 m, about 0.005 m to about 0.1 m, about 0.005 m to about 0.09 m,about 0.005 m to about 0.08 m, about 0.005 m to about 0.07 m, about0.005 m to about 0.06 m, about 0.005 m to about 0.05 m, about 0.005 m toabout 0.04 m, about 0.005 m to about 0.03 m, about 0.005 m to about 0.02m, or about 0.005 m to about 0.01 m.

In some embodiments, one or more stages of the humidifier and/ordehumidifier comprise one or more components configured to facilitate,direct, or otherwise affect flow of a fluid within the one or morestages.

For example, in some embodiments, one or more stages of the humidifierand/or dehumidifier comprise one or more weirs. As used herein, a weirrefers to a structure that obstructs liquid flow in a stage. In somecases, a weir may be positioned adjacent or surrounding a region whereliquid may flow out of stage, for example, into a different stage below.For example, if a weir is positioned upstream of a liquid outlet of astage, any additional liquid that would cause the height of a liquidlayer to exceed the height of the weir would flow over the weir and exitthe stage through the liquid outlet. In some embodiments, the maximumheight of a liquid layer in one or more stages of a humidifier and/ordehumidifier may be set by one or more weirs.

In some embodiments, one or more stages of the humidifier and/ordehumidifier comprise one or more baffles positioned to direct flow of aliquid stream within the one or more stages. Suitable baffles for use inembodiments described herein include plate-like articles having, forexample, a substantially rectangular shape. Baffles may also be referredto as barriers, dams, or the like. In some cases, the one or morebaffles can be arranged on a bottom surface of a stage such that liquidtravels in a substantially linear path from one end of the stage to theother end of the stage (e.g., along the length of a stage having asubstantially rectangular cross-section). In some cases, the one or morebaffles can be arranged such that liquid travels in a non-linear pathacross a chamber, such as a path having one or more bends or turnswithin the chamber. That is, the liquid may travel a distance within thestage that is longer than the length of the stage. In some embodiments,one or more baffles may be positioned substantially parallel to thetransverse sides (i.e., width) of a stage having a substantiallyrectangular cross-sectional shape, i.e., may be a transverse baffle. Insome embodiments, one or more baffles may be positioned substantiallyparallel to the longitudinal sides (i.e., length) of a stage having asubstantially rectangular cross-sectional shape, i.e., may be alongitudinal baffle. In such configurations, one or more longitudinalbaffles may direct the flow of liquid along a substantially non-linearpath. In some cases, it may be advantageous to increase the amount oftime a liquid spends flowing through a stage. Accordingly, in certainembodiments, one or more baffles may be positioned within a single stageto facilitate liquid flow along a flow path having a relatively highaspect ratio (e.g., the ratio of the average length of the flow path tothe average width of the flow path). For example, in some cases, one ormore baffles may be positioned such that liquid flowing through thestage follows a flow path having an aspect ratio of at least about 1.5,at least about 2, at least about 5, at least about 10, at least about20, at least about 50, at least about 75, at least about 100, or more.In some embodiments, liquid flowing through the stage follows a flowpath having an aspect ratio in the range of about 1.5 to about 5, about1.5 to about 10, about 1.5 to about 20, about 1.5 to about 50, about 1.5to about 75, about 1.5 to about 100, about 5 to about 10, about 5 toabout 20, about 5 to about 50, about 5 to about 75, about 5 to about100, about 10 to about 20, about 10 to about 50, about 10 to about 75,about 10 to about 100, or about 50 to about 100.

In some embodiments, the humidifier and/or dehumidifier comprise one ormore additional features to increase efficiency and/or production.Non-limiting examples of these features include stacks and/or dropleteliminators.

In certain embodiments, the humidifier and/or dehumidifier comprise anoptional stack. A stack generally refers to a structure (e.g., conduit)in fluid communication with a gas outlet of the humidifier and/ordehumidifier, where the maximum cross-sectional dimension (e.g.,diameter) and/or length of the stack is larger than the correspondingmaximum cross-sectional dimension and/or length of the gas outlet. Insome cases, a stack may reduce or eliminate droplet entrainment (e.g.,droplets of liquid flowing out of the humidifier and/or dehumidifierwith the gas stream).

In certain embodiments, the humidifier and/or dehumidifier comprise oneor more optional droplet eliminators. A droplet eliminator generallyrefers to a device or structure configured to prevent entrainment ofliquid droplets. Non-limiting examples of suitable types of dropleteliminators include mesh eliminators (e.g., wire mesh mist eliminators),vane eliminators (e.g., vertical flow chevron vane mist eliminators,horizontal flow chevron vane mist eliminators), cyclonic separators,vortex separators, droplet coalescers, and/or knockout drums. In somecases, the droplet eliminator may be configured such that liquiddroplets entrained in a gas stream collide with a portion of the dropleteliminator and fall out of the gas stream. In certain embodiments, thedroplet eliminator may extend across the opening (e.g., mouth) of one ormore gas outlets of a humidifier or dehumidifier. In some cases, adroplet eliminator may be positioned within a humidifier and/ordehumidifier upstream of a gas outlet of the humidifier and/ordehumidifier. In some cases, reducing or eliminating droplet entrainmentmay advantageously increase the amount of condensable fluid in liquidphase (e.g., purified water) recovered from a humidifier and/ordehumidifier (e.g., by reducing the amount of condensable fluid lostthrough a gas outlet).

In some embodiments, the humidifier and/or dehumidifier comprise one ormore intermediate gas inlets and/or intermediate gas outlets. In somecases, extraction of at least a portion of a gas flow from at least oneintermediate location in the humidifier and injection into at least oneintermediate location in the dehumidifier may be thermodynamicallyadvantageous. Because the portion of a gas flow exiting the humidifierat an intermediate gas outlet (e.g., the extracted portion) has notpassed through the entire humidifier, the temperature of the gas flow atthe intermediate gas outlet may be lower than the temperature of the gasflow at the main gas outlet of the humidifier. The locations of theintermediate extraction points (e.g., gas outlets) and/or injectionpoints (e.g., gas inlets) may be selected to increase the thermalefficiency of the system. For example, because a gas (e.g., air) mayhave increased vapor content at higher temperatures than at lowertemperatures, and because the specific enthalpy of a gas with highervapor content may be higher than the specific enthalpy of a gas withlower vapor content, less gas may be used in higher temperature areas ofthe humidifier and/or dehumidifier to better balance the heat capacityrate ratios of the gas (e.g., air) and liquid (e.g., water) streams.Extraction and/or injection of a portion of a gas flow at intermediatelocations may therefore advantageously allow for manipulation of gasmass flows and for greater heat recovery.

However, it should be recognized that in some embodiments, under certainoperating conditions, intermediate extraction and/or injection may notnecessarily or always increase the thermal efficiency of an HDH system.Additionally, there may be certain drawbacks associated with extractionand/or injection at intermediate locations in some situations. Forexample, intermediate extraction and/or injection may reduce thecondensable fluid (e.g., water) production rate of the system, and theremay be certain additional costs associated with intermediate extractionand/or injection (e.g., costs associated with instrumentation, ducting,insulation, and/or droplet separation). In some cases, if thetemperature difference between a gas flow at an intermediate injectionlocation in the dehumidifier and a gas flow extracted from thehumidifier and injected in the intermediate injection location is toogreat, production rates and/or energy efficiency may be decreased.Accordingly, in some cases, it may be advantageous to build and/oroperate an apparatus without intermediate extraction and/or injection.

The humidifier and/or dehumidifier may have any shape suitable for aparticular application. In some embodiments, the humidifier and/ordehumidifier have a cross-sectional shape that is substantiallycircular, substantially elliptical, substantially square, substantiallyrectangular, substantially triangular, or irregularly shaped. In someembodiments, the humidifier and/or dehumidifier have a relatively highcross-sectional aspect ratio. In certain cases, the humidifier and/ordehumidifier have a cross-sectional aspect ratio of at least about 1.5,at least about 2, at least about 5, at least about 10, at least about15, or at least about 20. In some embodiments, the humidifier and/ordehumidifier has an aspect ratio in the range of about 1.5 to about 5,about 1.5 to about 10, about 1.5 to about 15, about 1.5 to about 20,about 2 to about 5, about 2 to about 10, about 2 to about 15, about 2 toabout 20, about 5 to about 10, about 5 to about 15, about 5 to about 20,about 10 to about 15, about 10 to about 20, or about 15 to about 20. Incertain embodiments, the humidifier and/or dehumidifier have asubstantially parallelepiped shape, a substantially rectangularprismatic shape, a substantially cylindrical shape, a substantiallypyramidal shape, and/or an irregular shape.

The exterior of the humidifier and/or dehumidifier may comprise anysuitable material. In certain embodiments, the humidifier and/ordehumidifier comprise stainless steel, aluminum, and/or a plastic (e.g.,polyvinyl chloride, polyethylene, polycarbonate). In some embodiments,it may be advantageous to minimize heat loss from the humidifier and/ordehumidifier to the environment. In some cases, the exterior and/or theinterior of the humidifier and/or dehumidifier may comprise a thermallyinsulating material. For example, the humidifier and/or dehumidifier maybe at least partially coated, covered, or wrapped with a thermallyinsulating material. Non-limiting examples of suitable thermallyinsulating materials include elastomeric foam, fiberglass, ceramic fibermineral wool, glass mineral wool, phenolic foam, polyisocyanurate,polystyrene, and polyurethane.

In some cases, the humidifier and/or dehumidifier may have a relativelysmall size (e.g., relatively low height, relatively small footprint). Incertain cases, it may be advantageous for a humidifier and/ordehumidifier to have a relatively small size. For example, a relativelylow height and/or relatively small footprint may advantageouslyfacilitate shipping (e.g., because the humidifier and/or dehumidifiermay fit on existing truck beds) and/or installation of the humidifierand/or dehumidifier, particularly for systems located at remote sites.

In some embodiments, the humidifier and/or dehumidifier have arelatively low height. The height of a humidifier or dehumidifier mayrefer to the maximum vertical distance between a first end (e.g., a topend) and a second end (e.g., a bottom end) of the humidifier ordehumidifier. In some cases, the humidifier and/or dehumidifier have aheight of about 5 m or less, about 4 m or less, about 3.5 or less, about3 m or less, about 2 m or less, about 1 m or less, or, in some cases,about 0.5 m or less. In certain cases, the humidifier and/ordehumidifier have a height in the range of about 1 m to about 5 m, about1 m to about 4 m, about 1 m to about 3.5 m, about 1 m to about 3 m, orabout 1 m to about 2 m.

In some embodiments, the humidifier and/or dehumidifier have arelatively small footprint (e.g., surface area of a bottom surface ofthe humidifier and/or dehumidifier). In certain embodiments, thehumidifier and/or dehumidifier have a footprint of about 100 m² or less,about 75 m² or less, about 50 m² or less, about 20 m² or less, about 10m² or less, about 5 m² or less, about 2 m² or less, or about 1 m² orless. In some cases, the humidifier and/or dehumidifier have a footprintin the range of about 1 m² to about 100 m², about 1 m² to about 75 m²,about 1 m² to about 50 m², about 1 m² to about 20 m², about 1 m² toabout 10 m², or about 1 m² to about 5 m².

According to some embodiments, the humidifier and dehumidifier arehoused in separate vessels. In other embodiments, the humidifier anddehumidifier are housed within the same vessel. In some such cases, thehumidifier and dehumidifier may be vertically arranged (e.g., thedehumidifier positioned on top of the humidifier) or horizontallyarranged. Housing the humidifier and dehumidifier within the same vesselmay be advantageous in certain cases, as a combined HDH apparatus mayhave fewer components and/or use less material than an HDH systemcomprising a separate humidifier and dehumidifier.

In some embodiments, the humidifier and/or dehumidifier may be fluidlyconnected to one or more additional devices. For example, in someembodiments, the dehumidifier may be fluidically connected to anoptional external cooling device. The cooling device may, in some cases,also be fluidically connected to the second heat exchanger. In certainembodiments, the cooling device may be arranged such that a liquidstream (e.g., a dehumidifier liquid outlet stream, a cooled dehumidifierliquid outlet stream) is cooled in the cooling device prior to returningto the dehumidifier.

A cooling device generally refers to any device that is capable ofremoving heat from a fluid stream (e.g., a liquid stream, a gas stream).In some embodiments, the cooling device is a heat exchanger. The heatexchanger may be configured such that a first fluid stream and a secondfluid stream flow through the heat exchanger. In some cases, the firstfluid stream and the second fluid stream may flow in substantially thesame direction (e.g., parallel flow), substantially opposite directions(e.g., counter-flow), or substantially perpendicular directions (e.g.,cross flow). In some cases, heat is transferred from a first fluidstream to a second fluid stream. In certain embodiments, the coolingdevice is a liquid-to-gas heat exchanger. The first fluid stream may, incertain cases, comprise a fluid stream that is part of a loop ofcondenser liquid flowing between a condenser and a heat exchanger (e.g.,a dehumidifier liquid outlet stream). The second fluid stream may, insome cases, comprise a coolant. The coolant may be any fluid capable ofabsorbing or transferring heat. In some embodiments, the coolantcomprises a gas. The gas may, in some cases, comprise air (e.g., ambientair). Heat exchangers that comprise air as a coolant may generally bereferred to as air-cooled heat exchangers. In some cases, more than twofluid streams flow through the cooling device. In some embodiments, noneof the fluid streams flowing through cooling device may undergo a phasechange. It should also be noted that the cooling device may, in someembodiments, be a dry cooler, a chiller, a radiator, or any other devicecapable of removing heat from a fluid stream.

The cooling device may, in some cases, decrease the temperature of afluid stream (e.g., a dehumidifier liquid outlet stream). In someembodiments, the cooling device decreases the temperature of the fluidstream by at least about 5 ° C., at least about 10 ° C., at least about15 ° C., at least about 20 ° C., at least about 30 ° C., at least about40 ° C., at least about 50 ° C., at least about 60 ° C., at least about70 ° C., at least about 80 ° C., or, in some cases, at least about 90 °C. In some embodiments, the cooling device decreases the temperature ofthe fluid stream by an amount in the range of about 5 ° C. to about 30 °C., about 5 ° C. to about 60 ° C., about 5 ° C. to about 90 ° C., about10 ° C. to about 30 ° C., about 10 ° C. to about 60 ° C., about 10 ° C.to about 90 ° C., about 20 ° C. to about 30 ° C., about 20 ° C. to about60 ° C., about 20 ° C. to about 90 ° C., about 30 ° C. to about 60 ° C.,about 30 ° C. to about 90 ° C., or about 60 ° C. to about 90 ° C.

In some embodiments, the humidifier may be fluidically connected to anoptional pre-treatment system. In some cases, a pre-treatment system maybe configured to remove one or more components from an influent liquidstream entering the system. In some embodiments, the pre-treatmentsystem comprises an optional separation apparatus configured to removeat least a portion of a suspended and/or emulsified immiscible phasefrom a liquid stream. In some embodiments, the pre-treatment systemcomprises an optional ion-removal apparatus configured to remove atleast a portion of at least one scale-forming ion from a liquid stream.In some embodiments, the pre-treatment system comprises an optionalsuspended solids removal apparatus configured to remove at least aportion of suspended solids from a liquid stream. In some embodiments,the pre-treatment system comprises an optional pH adjustment apparatusconfigured to adjust (i.e. increase or decrease) or maintain/stabilize(e.g. via buffering) the pH of a liquid stream. In some embodiments, thepre-treatment system comprises an optional volatile organic material(VOM) removal apparatus configured to remove at least a portion of VOMfrom a liquid stream. In some embodiments, the pre-treatment systemcomprises an optional filtration apparatus configured to produce asubstantially solid material. Each component of the pre-treatment systemmay be fluidly connected to one or more other components ofpre-treatment system, either directly or indirectly.

In some embodiments, the humidifier may be fluidically connected to anoptional precipitation apparatus. In some cases, a precipitationapparatus may be configured to precipitate one or more solid salts froma concentrated liquid stream of the humidifier comprising a dissolvedsalt (e.g., a humidifier liquid outlet stream). In some cases, theprecipitation apparatus comprises a vessel, such as a settling tank. Insome embodiments, the settling tank comprises a low shear mixer. The lowshear mixer can be configured to keep the crystals that are formed mixed(e.g., homogeneously mixed) in the concentrated liquid stream. Accordingto certain embodiments, the vessel is sized such that there issufficient residence time for crystals to form and grow. In some cases,the precipitation apparatus comprises at least one vessel comprising avolume within which the concentrated liquid stream is substantiallyquiescent. In some embodiments, the flow velocity of the liquid streamwithin the substantially quiescent volume is less than the flow velocityat which precipitation (e.g., crystallization) is inhibited. Forexample, the liquid stream within the substantially quiescent volume mayhave, in certain embodiments, a flow velocity of zero. In someembodiments, the fluid within the substantially quiescent volume mayhave a flow velocity that is sufficiently high to suspend the formedsolids (e.g., crystals), but not sufficiently high to prevent solidformation (e.g., crystal nucleation). The substantially quiescent volumewithin the vessel may occupy, in some embodiments, at least about 1%, atleast about 5%, at least about 10%, or at least about 25% of the volumeof the vessel. As one particular example, the precipitation apparatuscan comprise a vessel including a stagnation zone. The stagnation zonemay be positioned, for example, at the bottom of the precipitationvessel.

In certain embodiments, the precipitation apparatus can include a secondvessel in which the solids precipitated in the first vessel are allowedto settle. For example, an aqueous stream containing the precipitatedsolids can be transported to a settling tank, where the solids can beallowed to settle. The remaining contents of the aqueous stream can betransported out of the settling tank. While the use of two vesselswithin the precipitation apparatus has been described, it should beunderstood that, in other embodiments, a single vessel, or more than twovessels may be employed. In certain embodiments, the system can beoperated such that precipitation of the salt occurs substantially onlywithin the stagnation zone of the precipitation vessel.

In some embodiments, the precipitated salt from the precipitationapparatus is fed to a solids-handling apparatus. The solids-handlingapparatus may be configured, in certain embodiments, to remove at leasta portion of the water retained by the precipitated salt. In some suchembodiments, the solids-handling apparatus is configured to produce acake comprising at least a portion of the precipitated salt from theprecipitation apparatus. As one example, the solids-handling apparatuscan comprise a filter (e.g., a vacuum drum filter or a filter press)configured to at least partially separate the precipitated salt from theremainder of a suspension containing the precipitated salt. In some suchembodiments, at least a portion of the liquid within the salt suspensioncan be transported through the filter, leaving behind solid precipitatedsalt.

Appropriate conditions under which to operate the systems (e.g., HDHsystems) described herein for desired performance may be selected by anoperator of the system and/or by an algorithm. In some embodiments, thepressure in the humidifier and/or dehumidifier may be selected to beapproximately ambient atmospheric pressure during operation. Accordingto certain embodiments, the pressure in the humidifier and/ordehumidifier may be selected to be about 90 kPa or less duringoperation. It may be desirable, in some embodiments, for the pressure inthe humidifier to be less than approximately ambient atmosphericpressure during operation. In some cases, as the pressure inside thehumidifier decreases, the ability of the humidified carrier gas to carrymore water vapor increases, allowing for increased production ofsubstantially pure water when the carrier gas is dehumidified in thedehumidifier. Without wishing to be bound by a particular theory, thiseffect may be explained by the humidity ratio, which generally refers tothe ratio of water vapor mass to dry air mass in moist air, being higherat pressures lower than atmospheric pressure.

In some embodiments, the humidifier and/or dehumidifier may have arelatively low pressure drop during operation. As used herein, thepressure drop across a humidifier or dehumidifier refers to thedifference between the pressure of a gas stream entering the humidifieror dehumidifier at a main gas inlet and the pressure of a gas streamexiting the humidifier or dehumidifier at a main gas outlet. In somecases, the pressure drop may not include the effect ofpressure-increasing devices (e.g., fans, blowers, compressors, pumps).For example, in certain cases, the pressure drop may be obtained bysubtracting the effect of one or more pressure-increasing devices on agas stream from the difference between the pressure of the gas streamentering the humidifier or dehumidifier at a main gas inlet and thepressure of the gas stream exiting the humidifier or dehumidifier at amain gas outlet. In some embodiments, the pressure drop across thehumidifier or dehumidifier is about 100 kPa or less, about 75 kPa orless, about 50 kPa or less, about 20 kPa or less, about 15 kPa or less,about 10 kPa or less, about 5 kPa or less, about 2 kPa or less, or about1 kPa or less. In certain embodiments, the pressure drop across thehumidifier or dehumidifier (e.g., difference in pressure between themain gas outlet and the main gas inlet) is in the range of about 1 kPato about 2 kPa, about 1 kPa to about 5 kPa, about 1 kPa to about 10 kPa,about 1 kPa to about 15 kPa, about 1 kPa to about 20 kPa, about 1 kPa toabout 50 kPa, about 1 kPa to about 75 kPa, or about 1 kPa to about 100kPa. In some embodiments, the pressure drop is substantially zero.

According to some embodiments, systems described herein (e.g., HDHsystems) are substantially continuously operated and/or configured tofacilitate substantially continuous operation. As used herein, acontinuously-operated system refers to a system in which an influentliquid stream is fed to the system at the same rate that a condensableliquid stream is produced by the system. In some cases, one or moreliquid streams within the system may be in substantially continuousmotion. For example, for a bubble column HDH system, an influent liquidstream may be fed to a component of the system (e.g., a second heatexchanger, a heating device, a humidifier, a dehumidifier),substantially continuously flow through one or more stages of thehumidifier or dehumidifier of the system, and result in production of acondensable liquid stream (e.g., a substantially pure water stream). Insome cases, a continuously-operated system may be associated withcertain advantages, including, but not limited to, increased uptimeand/or enhanced energy performance.

In some embodiments, the system (e.g., HDH system) is substantiallytransiently operated and/or configured to facilitate substantiallytransient operation (e.g., batch processing). As used herein, atransiently-operated system refers to a system in which an amount ofliquid (e.g., salt-containing water) is introduced into the system andremains in the system until a certain condition (e.g., a certainsalinity, a certain density) is reached. Upon satisfaction of thecondition, the liquid is discharged from the apparatus. In certaincases, transient operation may allow cleaning operations to beinterspersed with production operations. For example, transientoperation may be advantageous for systems comprising filter presses,bioreactors, and/or other systems that may require periodic cleaning. Insome cases, transient operation may advantageously facilitate processingof highly viscous liquids (e.g., sugar-containing feedstock) that may bedifficult to pump.

It should be noted that while the systems (e.g., HDH systems) describedherein have generally been discussed in the context of desalinationsystems, the systems may be used in other types of systems (e.g., otherwater treatment/purification systems). For example, the describedsystems may be used in separation processes to separate one or morecomponents of an input liquid stream (e.g., a liquid mixture). In aparticular, non-limiting embodiment, the described systems may be usedin distillation systems to distill certain liquids from liquid mixtures(e.g., ionic solutions). Examples of liquids that may be distilled fromliquid mixtures using the systems described herein include, but are notlimited to, ammonia, benzene, toluene, phenol, xylene, naphthalene,xylene, gasoline, methanol, ethanol, propanol, butanol, isopropylalcohol, propylene glycol, hexane-n, heptane-n, octane-n, cyclohexane,acetic acid, formic acid, nitric acid, carbon tetrachloride, methylacetate, and/or acetone.

Various of the components described herein can be “directly fluidlyconnected” to other components. As used herein, a direct fluidconnection exists between a first component and a second component (andthe two components are said to be “directly fluidly connected” to eachother) when they are fluidly connected to each other and the compositionof the fluid does not substantially change (i.e., no fluid componentchanges in relative abundance by more than 5% and no phase changeoccurs) as it is transported from the first component to the secondcomponent. As an illustrative example, a stream that connects first andsecond system components, and in which the pressure and temperature ofthe fluid is adjusted but the composition of the fluid is not altered,would be said to directly fluidly connect the first and secondcomponents. If, on the other hand, a separation step is performed and/ora chemical reaction is performed that substantially alters thecomposition of the stream contents during passage from the firstcomponent to the second component, the stream would not be said todirectly fluidly connect the first and second components.

Other examples of HDH systems are described in U.S. Pat. No. 8,292,272,by Elsharqawy et al., issued Oct. 23, 2012, entitled “Water SeparationUnder Reduced Pressure”; U.S. Pat. No. 8,465,006, by Elsharqawy et al.,issued Jun. 18, 2013, entitled “Separation of a Vaporizable ComponentUnder Reduced Pressure”; U.S. Pat. No. 8,252,092, by Govindan et al.,issued Aug. 28, 2012, entitled “Water Separation Under Varied Pressure”;U.S. Pat. No. 8,496,234, by Govindan et al., issued Jul. 30, 2013,entitled “Thermodynamic Balancing of Combined Heat and Mass ExchangeDevices”; U.S. Pat. No. 8,523,985, by Govindan et al., issued Sep. 3,2013, entitled “Bubble-Column Vapor Mixture Condenser”; U.S. Pat. No.8,778,065, by Govindan et al., issued Jul. 15, 2014, entitled“Humidification-Dehumidification System Including a Bubble-Column VaporMixture Condenser”; U.S. Pat. No. 9,072,984, by Govindan et al., issuedJul. 7, 2015, entitled “Bubble-Column Vapor Mixture Condenser”; U.S.Patent Publication No. 2015/0129410, by Govindan et al., filed Sep. 12,2014, entitled “Systems Including a Condensing Apparatus Such as aBubble Column Condenser”; and International Patent Publication No. WO2014/200829, by Govindan et al., filed Jun. 6, 2014, as InternationalPatent Application No. PCT/US2014/041226, and entitled “Multi-StageBubble Column Humidifier,” the contents of all of which are incorporatedherein by reference in their entireties for all purposes.

EXAMPLE

In this Example, an HDH system comprising a bubble column humidifier anda bubble column condenser is described. The system contained five fluidpaths: an air flow path, a main brine flow path, a top trayrecirculation flow path, a heated liquid flow path associated with anelectric heater, and a pure water flow path.

FIG. 4 is a schematic diagram of the HDH system. The system comprised amulti-stage bubble column humidifier 402, a multi-stage bubble columncondenser 422, an electric heater 404, a titanium plate-and-frame heatexchanger 432, an air-cooled heat exchanger 444, and a storage tank 434.Bubble column humidifier 402 comprised a plurality of stages comprisingfirst stage 402A, last stage 402H, and intermediate stages 402B-402G. Inaddition, bubble column humidifier 402 comprised sump volume 4021positioned below stages 402A-402H. Bubble column condenser 422 compriseda plurality of stages comprising first stage 422A, last stage 422H, andintermediate stages 422B-422G. In addition, bubble column condenser 422comprised sump volume 4221 positioned below stages 422A-422H.

The system comprised an air flow path. At a main humidifier air inlet ofhumidifier 402, a blower forced air stream 412 to enter humidifier 402.Air stream 412 flowed through humidifier 402 from last stage 402H tofirst stage 402A, and as air stream 412 flowed through humidifier 402,heat and mass were transferred to air stream 412 from a liquid stream toproduce a humidified air stream. The humidified air stream exitedhumidifier 402 through a main humidifier gas outlet as vapor-containinghumidifier gas outlet stream 414. Stream 414 was directed to flow tobubble column condenser 422. In bubble column condenser 422, stream 414flowed from last stage 422H to first stage 422A. Within bubble columncondenser 422, heat and mass were transferred from vapor-containinghumidifier gas outlet stream 414 to a liquid stream to produce adehumidified gas stream. The dehumidified gas stream was discharged fromdehumidifier 422 through a main dehumidifier gas outlet as dehumidifiergas outlet stream 426.

The flow of the air stream through the air flow path was controlled bythe blower's variable frequency drive (VFD), which set the speed of theblower's rotation. The flow rate of the air stream was measured at theoutlet of the blower by a pitot tube.

Brine was circulated through the system along two connected flow paths:a main flow path, which circulated through all eight trays of humidifier402, and a top tray recirculation flow path.

The main flow path included all eight trays of humidifier 402, aVFD-controlled pump, energy recovery heat exchanger 432, and heatingdevice 404, which added thermal energy to the system. Volumetric flowrate was measured by a paddle wheel flow meter, and temperature wasmeasured by type K thermocouples. A feedback control system maintainedthe temperature of the brine entering humidifier 402 at a substantiallyconstant temperature. The feedback control system adjusted the rate ofthe heating fluid stream flowing through a second fluidic pathway ofheating device 404 in order to heat the brine to a selected temperatureprior to entering humidifier 402.

The top tray recirculation flow path included heating device 404, firststage 402A of humidifier 402, storage tank 434, and a VFD-controlledpump. The recirculation flow was injected into the main flow through atee between heat exchanger 432 and heating device 404. The combined flowwas heated in heating device 404, then partially cooled and concentratedin first stage 402A of the humidifier 402. After flowing through firststage 402A, a portion 410 of the combined flow was extracted fromhumidifier 402 through a secondary humidifier liquid outlet, whichgravity fed to storage tank 434. During operation, the extraction flowwas matched with the injection flow by controlling the extraction ratewith a gate valve and the injection rate through the pump's VFD.

The pure water flow path included bubble column condenser 422, aVFD-controlled pump, energy recovery heat exchanger 432, and air-cooledheat exchanger 444. A partial bypass of air-cooled heat exchanger 444was controlled with a gate valve, which controlled temperature intobubble column condenser 422.

The effect of top tray recirculation was measured by first bringing theHDH system to steady-state, balanced conditions with no recirculation,then successively lowering the heated brine temperature andcorrespondingly increasing the top tray recirculation rate to maintain aconstant enthalpy change across the top tray. The humidifier wasinitially balanced for a top temperature of 180° F.

Under the initial steady-state conditions, the air inlet flow rate was44.4 ACFM, the brine flow rate was 3 gpm, and the pure water flow ratewas 3 gpm. The temperatures at the fluid inlets and outlets of thehumidifier and dehumidifier are shown in Table 1.

TABLE 1 Location Temperature (° F.) Humidifier brine inlet 180Humidifier air inlet 136 Humidifier brine outlet 124 Humidifier airoutlet 167 Top tray temperature 166 Dehumidifier pure water inlet 127Dehumidifier air inlet 167 Dehumidifier pure water outlet 166Dehumidifier air outlet 125

Top tray recirculation was then introduced, and the temperature ofheated combined stream 408 exiting heating device 404 was reducedaccording to Table 2. Rates were calculated such that the temperature ofthe brine and air exiting first stage 402A would be unchanged. All otherflow rates were maintained. Extraction and injection flow rates werematched.

TABLE 2 Set Point Temperature (° F.) Recirculation Rate (gpm) 180 0 1780.5 177 1 175 2 174 3

Once the system reached steady state at each of the above 5 points,temperatures and flow rates were recorded. Two sets of data werecollected for each temperature and flow rate combination.

In addition, the experiment was repeated using a higher top brinetemperature of 192° F. Under the second set of conditions, the air inletflow rate was 44.4 ACFM, the brine flow rate was 4 gpm, and the purewater flow rate was 4 pm. The initial temperatures are shown in Table 3.

TABLE 3 Location Temperature (° F.) Humidifier brine inlet 192Humidifier air inlet 149 Humidifier brine outlet 134 Humidifier airoutlet 177 Top tray temperature 176 Dehumidifier pure water inlet 139Dehumidifier air inlet 177 Dehumidifier pure water outlet 172Dehumidifier air outlet 139

The brine inlet temperatures and corresponding top tray recirculationflow rates, which were selected to maintain a constant brine enthalpychange, are shown in Table 4.

TABLE 4 Set Point Temperature (° F.) Recirculation Rate (gpm) 192 0 1891 187 2 185 3 184 4 183 5 182 6

It was found that the humidifier air outlet temperature was relativelyunchanged at different top brine temperatures. The invariancedemonstrated that flow rate and temperature, individually, do not have astrong effect on heat transfer in a bubble column. The constant airtemperature corresponded to a constant enthalpy transfer from the brine,as shown in Table 5. While there was some variance in the enthalpytransfer rate, the variance was on the same order as the enthalpyvariance in the humidified air. Small changes in humidified airtemperature corresponded to a large change in the enthalpy of thehumidified air due to the change in vapor capacity and latent heatcontained therein.

TABLE 5 Influent brine flow Influent brine Effluent brine Enthalpytransfer rate (gpm) temperature (° F.) temperature (° F.) rate (BTU/h) 3180 166 341 3 180 167 314 3.5 178 169 240 3.5 179 168 287 4 176 167 2924 177 168 293 5 175 168 281 5 175 168 299 6 173 169 227 6 173 168 257

The temperature of brine exiting second stage 402B was also measured toevaluate the effect of top tray extraction and recirculation on the restof humidifier 402 (i.e., stages 402B-402H). It was found that thetemperature was relatively constant, indicating similarly constantinfluent conditions to the lower sections of humidifier 402. Theinvariance demonstrated that the top tray recirculation had littleeffect on downstream stages.

In addition, production rate and gained output ratio (GOR) werecalculated. Production rate was calculated from the product of the massflow of the air and the difference in humidity ratios between thedehumidifier's influent and effluent air streams. Gained output ratio(GOR) was calculated as the quotient of the production rate and theenthalpy transfer rate across heating device 404, expressed as anequivalent mass rate of steam. GOR is an energy efficiency metric,frequently used to compare thermal desalination processes, which isapproximately equal to the number of times a unit of thermal energy isused and recycled in a system.

In FIG. 5A, the effect of top tray recirculation on production rate,GOR, and top brine temperature is shown. Each value was normalized bythe respective value under the initial steady state conditions. Therelative invariance of production rate, GOR, and top brine temperatureshown in FIG. 5A demonstrated that top tray recirculation could be usedto reduce humidifier inlet temperature without sacrificing production orthermal efficiency.

The conclusions were supported by the higher temperature experiment.FIG. 5B shows the effect of top tray recirculation on production rate,GOR, and top brine temperature in the higher temperature (192° F.)experiment. FIG. 5B also demonstrated relative invariance of productionrate, GOR, and top brine temperature.

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,and/or methods, if such features, systems, articles, materials, and/ormethods are not mutually inconsistent, is included within the scope ofthe present invention.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Other elements may optionallybe present other than the elements specifically identified by the“and/or” clause, whether related or unrelated to those elementsspecifically identified unless clearly indicated to the contrary. Thus,as a non-limiting example, a reference to “A and/or B,” when used inconjunction with open-ended language such as “comprising” can refer, inone embodiment, to A without B (optionally including elements other thanB); in another embodiment, to B without A (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of' or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc. In theclaims, as well as in the specification above, all transitional phrasessuch as “comprising,” “including,” “carrying,” “having,” “containing,”“involving,” “holding,” and the like are to be understood to beopen-ended, i.e., to mean including but not limited to. Only thetransitional phrases “consisting of' and “consisting essentially ofshall be closed or semi-closed transitional phrases, respectively.

In cases where the present specification and a document incorporated byreference, attached as an appendix, and/or referred to herein includeconflicting disclosure, and/or inconsistent use of terminology, and/orthe incorporated/appended/referenced documents use or define termsdifferently than they are used or defined in the present specification,the present specification shall control.

What is claimed is:
 1. A humidifier system, comprising: a humidifiercomprising a main humidifier liquid inlet, a main humidifier gas inlet,a main humidifier liquid outlet, an intermediate humidifier liquidoutlet, a main humidifier gas outlet, and a plurality of stages, whereinthe plurality of stages comprises a first stage, a last stage, and oneor more intermediate stages positioned between the first stage and thelast stage, wherein the intermediate humidifier liquid outlet is aliquid outlet of the first stage or one of the one or more intermediatestages; and a first heating device, wherein a first liquid inlet of thefirst heating device comprises or is fluidically connected to theintermediate humidifier liquid outlet, and wherein a first liquid outletof the first heating device comprises or is fluidically connected to themain humidifier liquid inlet, and wherein the first liquid inlet of thefirst heating device is configured to receive a first liquid streamcomprising a condensable fluid in liquid phase and a dissolved salt, andwherein the main humidifier gas inlet is configured to receive a gasstream comprising a non-condensable gas. 2-89. (canceled)
 90. Thehumidifier system according to claim 1, wherein the humidifier isconfigured to produce a vapor-containing humidifier gas outlet streamenriched in the condensable fluid in vapor phase relative to the gasstream received by the main humidifier gas inlet.
 91. The humidifiersystem according to claim 1, wherein the humidifier is configured toproduce a concentrated humidifier liquid outlet stream enriched in thedissolved salt relative to the first liquid stream received by the firstheating device.
 92. The humidifier system according to claim 1, whereinthe humidifier system forms part of a desalination system.
 93. Thehumidifier system according to claim 1, wherein the humidifier is abubble column humidifier.
 94. The humidifier system according to claim1, wherein: the first stage is the stage of the plurality of stagespositioned in closest proximity to the main humidifier liquid inlet, andthe last stage is the stage of the plurality of stages positioned inclosest proximity to the main humidifier liquid outlet.
 95. Thehumidifier system according to claim 1, wherein: the humidifier isconfigured to flow the first liquid stream in a first direction from thefirst stage to the last stage, and the humidifier is configured tosimultaneously flow the gas stream in a second direction from the laststage to the first stage.
 96. The humidifier system according to claim1, wherein: the humidifier further comprises an intermediate humidifierliquid inlet, and the intermediate humidifier liquid inlet is a liquidinlet of the first stage or one of the one or more intermediate stagesof the humidifier.
 97. The humidifier system according to claim 1,wherein the humidifier receives the first liquid stream at a temperatureof about 90° C. or less at the main humidifier liquid inlet.
 98. Thehumidifier system according to claim 91, wherein an extracted liquidstream exits the humidifier through the intermediate humidifier liquidoutlet at an extracted liquid stream flow rate and the concentratedhumidifier liquid outlet stream exits the humidifier through the mainhumidifier liquid outlet at a main humidifier liquid stream flow rate,wherein the extracted liquid stream flow rate is about 5% to 50% of themain humidifier liquid stream flow rate, when the humidifier system isin operation.
 99. The humidifier system according to claim 91, whereinan extracted liquid stream exits the humidifier through the intermediatehumidifier liquid outlet at an extracted liquid stream flow rate and theconcentrated humidifier liquid outlet stream exits the humidifierthrough the main humidifier liquid outlet at a main humidifier liquidstream flow rate, wherein the extracted liquid stream flow rate is about105% to 150% of the main humidifier liquid stream flow rate, when thehumidifier system is in operation.
 100. The humidifier system accordingto claim 1, further comprising a dehumidifier comprising a maindehumidifier gas inlet comprising or fluidically connected to the mainhumidifier gas outlet, and further comprising a main dehumidifier liquidinlet, a main dehumidifier gas outlet, and a main dehumidifier liquidoutlet.
 101. The humidifier system according to claim 100, wherein thedehumidifier is configured to remove at least a portion of thecondensable fluid in vapor phase from the vapor-containing humidifiergas outlet stream to produce a dehumidifier liquid outlet streamcomprising the condensable fluid in liquid phase and a dehumidifier gasoutlet stream lean in the condensable fluid in vapor phase relative tothe vapor-containing humidifier gas outlet stream.
 102. The humidifiersystem according to claim 100, wherein the dehumidifier is a bubblecolumn condenser.
 103. The humidifier system according to claim 1,wherein the first liquid inlet of the first heating device isfluidically connected to a source of the first liquid stream.
 104. Thehumidifier system according to claim 1, wherein the first heating deviceis a first heat exchanger.
 105. The humidifier system according to claim104, wherein: the first heat exchanger comprises a first fluidic pathwayand a second fluidic pathway, the first liquid inlet of the first heatexchanger is a liquid inlet of the first fluidic pathway, and the firstliquid outlet of the first heat exchanger is a liquid outlet of thefirst fluidic pathway.
 106. The humidifier system according to claim105, wherein the first heat exchanger is configured to transfer heatfrom a heating fluid stream flowing through the second fluidic pathwayto a liquid stream flowing through the first fluidic pathway.
 107. Thehumidifier system according to claim 106, wherein the heating fluidstream comprises water.
 108. The humidifier system according to claim 1,wherein the first heating device is a heat collection device, anelectric heater, or a furnace.
 109. The humidifier system according toclaim 100, further comprising a second heating device fluidicallyconnected to the first heating device and the dehumidifier.
 110. Thehumidifier system according to claim 109, wherein the second heatingdevice is a second heat exchanger comprising a first fluidic pathway anda second fluidic pathway, wherein a liquid inlet of the second fluidicpathway of the second heat exchanger is fluidically connected to themain dehumidifier liquid outlet.
 111. The humidifier system according toclaim 110, wherein a liquid outlet of the first fluidic pathway of thesecond heat exchanger is fluidically connected to an intermediatehumidifier liquid inlet, wherein the intermediate humidifier liquidinlet is a liquid inlet of one of the one or more intermediate stages ofthe humidifier.
 112. The humidifier system according to claim 1, furthercomprising a first tank fluidically connected to the intermediatehumidifier liquid outlet and the first liquid inlet of the first heatingdevice.
 113. The humidifier system according to claim 1, wherein thecondensable fluid comprises water.
 114. The humidifier system accordingto claim 1, wherein the non-condensable gas comprises air.
 115. Thehumidifier system according to claim 1, wherein the dissolved saltcomprises NaCl.